addr2line.c: do not suppress -Wpedantic

because it was for "-assi -Wpedantic" on Travis, but we changed the
Travis build to "-std=c99 -Wpedantic".

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@66786 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

addr2line.c

@@ -9,10 +9,7 @@
 **********************************************************************/
 
 #if defined(__clang__)
-#pragma clang diagnostic ignored "-Wpedantic"
 #pragma clang diagnostic ignored "-Wgcc-compat"
-#elif defined(__GNUC__)
-#pragma GCC diagnostic ignored "-Wpedantic"
 #endif
 
 #include "ruby/config.h"