[PATCH] Remove obsolete gcc pragma

[Brendan O'Dea]

Remove a pragma from perl.xs which gcc no longer recognises.

This pragma was meant to reduce noise, but now adds more.  Compiling
with gcc 11 produces:

  ../../perl.xs:24:32: warning: unknown option after ‘#pragma GCC diagnostic’ 
kind [-Wpragmas]
     24 | #pragma GCC diagnostic ignored "-Wcompound-token-split-by-macro"
        |                                ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

diff --git a/perl.xs b/perl.xs
index 646f2ed..86c04e3 100644
--- a/perl.xs
+++ b/perl.xs
@@ -21,7 +21,6 @@
  */
 #ifdef __GNUC__
 #pragma GCC diagnostic ignored "-Wcast-qual"
-#pragma GCC diagnostic ignored "-Wcompound-token-split-by-macro"
 #pragma GCC diagnostic ignored "-Wconversion"
 #pragma GCC diagnostic ignored "-Wnested-externs"
 #pragma GCC diagnostic ignored "-Wshadow"