pythongh-121040: Remove fallthrough warnings compiler option (pythongh-121041)

Remove fallthrough warnings

Author: nohlson

configure

@@ -2453,7 +2453,6 @@ AS_VAR_IF([with_strict_overflow], [yes],
 
 # Enable flags that warn and protect for potential security vulnerabilities.
 # These flags should be enabled by default for all builds.
-AX_CHECK_COMPILE_FLAG([-Wimplicit-fallthrough], [BASECFLAGS="$BASECFLAGS -Wimplicit-fallthrough"], [AC_MSG_WARN([-Wimplicit-fallthrough not supported])], [-Werror])
 AX_CHECK_COMPILE_FLAG([-fstack-protector-strong], [BASECFLAGS="$BASECFLAGS -fstack-protector-strong"], [AC_MSG_WARN([-fstack-protector-strong not supported])], [-Werror])
 AX_CHECK_COMPILE_FLAG([-Wtrampolines], [BASECFLAGS="$BASECFLAGS -Wtrampolines"], [AC_MSG_WARN([-Wtrampolines not supported])], [-Werror])