configure: remove backwards-compatibility code

The cmd_line.txt mangling is only needed when rebuilding from very old
trees and is kept mostly as an example of how to extend it.  However,
Meson 0.63 introduces a deprecation mechanism for meson_options.txt
that can be used instead, so get rid of our home-grown hack.

Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

configure

@@ -2568,16 +2568,6 @@ if test "$skip_meson" = no; then
   if test "$?" -ne 0 ; then
       error_exit "meson setup failed"
   fi
-else
-  if test -f meson-private/cmd_line.txt; then
-    # Adjust old command line options whose type was changed
-    # Avoids having to use "setup --wipe" when Meson is upgraded
-    perl -i -ne '
-      s/^gettext = true$/gettext = auto/;
-      s/^gettext = false$/gettext = disabled/;
-      /^b_staticpic/ && next;
-      print;' meson-private/cmd_line.txt
-  fi
 fi
 
 # Save the configure command line for later reuse.