x11-wm/piewm: fix the build with LLVM 11
This patch de-extern'd yylineno to actually cause the build failure that
popped up with the new -fno-common default that debuted in LLVM 11 and GCC
- Simply remove the patch to fix the build.
PR: 248859
MFH: 2020Q3 (-fno-common build fix)