libstdc++: Remove dg-options "-std=gnu++20" from std::format tests

The testsuite will automatically select C++20 for these tests now, and
removing the hardcoded -std option allows them to be tested for C++23
and C++26 as well.

libstdc++-v3/ChangeLog:

	* testsuite/std/format/arguments/args.cc: Remove dg-options.
	* testsuite/std/format/arguments/lwg3810.cc: Likewise.
	* testsuite/std/format/error.cc: Likewise.
	* testsuite/std/format/format_string.cc: Likewise.
	* testsuite/std/format/formatter/concept.cc: Likewise.
	* testsuite/std/format/formatter/ext_float.cc: Likewise.
	* testsuite/std/format/formatter/requirements.cc: Likewise.
	* testsuite/std/format/functions/107871.cc: Likewise.
	* testsuite/std/format/functions/format.cc: Likewise.
	* testsuite/std/format/functions/format_to.cc: Likewise.
	* testsuite/std/format/functions/format_to_n.cc: Likewise.
	* testsuite/std/format/functions/size.cc: Likewise.
	* testsuite/std/format/functions/vformat_to.cc: Likewise.
	* testsuite/std/format/parse_ctx.cc: Likewise.
	* testsuite/std/format/string.cc: Likewise.
	* testsuite/std/format/string_neg.cc: Likewise.
	* testsuite/std/format/functions/format_c++23.cc: Removed.

libstdc++-v3/testsuite/std/format/arguments/args.cc

@@ -1,4 +1,3 @@
-// { dg-options "-std=gnu++20" }
 // { dg-do run { target c++20 } }
 
 #include <format>

libstdc++-v3/testsuite/std/format/arguments/lwg3810.cc

@@ -1,4 +1,3 @@
-// { dg-options "-std=gnu++20" }
 // { dg-do compile { target c++20 } }
 
 // LWG 3810. CTAD for std::basic_format_args

libstdc++-v3/testsuite/std/format/error.cc

@@ -1,4 +1,3 @@
-// { dg-options "-std=gnu++20" }
 // { dg-do run { target c++20 } }
 
 #include <format>

libstdc++-v3/testsuite/std/format/format_string.cc

@@ -1,4 +1,3 @@
-// { dg-options "-std=gnu++20" }
 // { dg-do compile { target c++20 } }
 
 #include <format>

libstdc++-v3/testsuite/std/format/formatter/concept.cc

@@ -1,4 +1,3 @@
-// { dg-options "-std=gnu++23" }
 // { dg-do compile { target c++23 } }
 
 #include <format>

libstdc++-v3/testsuite/std/format/formatter/ext_float.cc

@@ -1,4 +1,3 @@
-// { dg-options "-std=gnu++20" }
 // { dg-do run { target c++20 } }
 
 #include <format>

libstdc++-v3/testsuite/std/format/formatter/requirements.cc

@@ -1,4 +1,3 @@
-// { dg-options "-std=gnu++20" }
 // { dg-do run { target c++20 } }
 
 #include <format>

libstdc++-v3/testsuite/std/format/functions/107871.cc

@@ -1,4 +1,3 @@
-// { dg-options "-std=gnu++20" }
 // { dg-do compile { target c++20 } }
 
 #include <format>

libstdc++-v3/testsuite/std/format/functions/format.cc

@@ -1,4 +1,3 @@
-// { dg-options "-std=gnu++20" }
 // { dg-do run { target c++20 } }
 // { dg-add-options no_pch }
 

libstdc++-v3/testsuite/std/format/functions/format_c++23.cc

@@ -1,5 +0,0 @@
-// { dg-do run { target c++23 } }
-// { dg-add-options no_pch }
-// This test does not have -std=gnu++20 in dg-options so that format.cc
-// can be tested for e.g. -std=c++26
-#include "format.cc"

libstdc++-v3/testsuite/std/format/functions/format_to.cc

@@ -1,4 +1,3 @@
-// { dg-options "-std=gnu++20" }
 // { dg-do run { target c++20 } }
 
 #include <format>

libstdc++-v3/testsuite/std/format/functions/format_to_n.cc

@@ -1,4 +1,3 @@
-// { dg-options "-std=gnu++20" }
 // { dg-do run { target c++20 } }
 
 #include <format>

libstdc++-v3/testsuite/std/format/functions/size.cc

@@ -1,4 +1,3 @@
-// { dg-options "-std=gnu++20" }
 // { dg-do run { target c++20 } }
 
 #include <format>

libstdc++-v3/testsuite/std/format/functions/vformat_to.cc

@@ -1,4 +1,3 @@
-// { dg-options "-std=gnu++20" }
 // { dg-do run { target c++20 } }
 
 #include <format>

libstdc++-v3/testsuite/std/format/parse_ctx.cc

@@ -1,4 +1,3 @@
-// { dg-options "-std=gnu++20" }
 // { dg-do run { target c++20 } }
 
 #include <format>

libstdc++-v3/testsuite/std/format/string.cc

@@ -1,4 +1,3 @@
-// { dg-options "-std=gnu++20" }
 // { dg-do run { target c++20 } }
 
 #include <format>

libstdc++-v3/testsuite/std/format/string_neg.cc

@@ -1,4 +1,3 @@
-// { dg-options "-std=gnu++20" }
 // { dg-do compile { target c++20 } }
 
 #include <format>