RISC-V: Update testcases info with new implement info

After commit 591b6e00d1 " riscv: fix -Wformat-diag errors ", some strings in implement was changed.
    This patch update the check info in testcases to sync with it.

gcc/testsuite/ChangeLog:

	* gcc.target/riscv/arch-9.c: Update the check info.
	* gcc.target/riscv/arch-10.c: Ditto.
	* gcc.target/riscv/arch-12.c: Ditto.

gcc/testsuite/gcc.target/riscv/arch-10.c

@@ -3,4 +3,4 @@
 int foo()
 {
 }
-/* { dg-error "Extension `f' appear more than one time." "" { target *-*-* } 0 } */
+/* { dg-error "extension 'f' appear more than one time" "" { target *-*-* } 0 } */

gcc/testsuite/gcc.target/riscv/arch-12.c

@@ -1,4 +1,4 @@
 /* { dg-do compile } */
 /* { dg-options "-O2 -march=rv64im1p2p3 -mabi=lp64" } */
 int foo() {}
-/* { dg-error "'-march=rv64im1p2p3': For 'm1p2p\\?', version number with more than 2 level is not supported." "" { target *-*-* } 0 } */
+/* { dg-error "'-march=rv64im1p2p3': for 'm1p2p\\?', version number with more than 2 level is not supported" "" { target *-*-* } 0 } */

gcc/testsuite/gcc.target/riscv/arch-9.c

@@ -3,4 +3,4 @@
 int foo()
 {
 }
-/* { dg-warning "version of `g` will be omitted, please specify version for individual extension." "" { target *-*-* } 0 } */
+/* { dg-warning "version of 'g' will be omitted, please specify version for individual extension" "" { target *-*-* } 0 } */