Remove ctime.timespec.compile.pass.cpp xfail

This test was failing because picolibc did not define TIME_UTC, but more
recent versions do now do this.

Author: dcandler

libcxx/test/std/language.support/support.runtime/ctime.timespec.compile.pass.cpp

@@ -11,9 +11,6 @@
 
 // UNSUPPORTED: c++03, c++11, c++14
 
-// picolibc doesn't define TIME_UTC.
-// XFAIL: LIBCXX-PICOLIBC-FIXME
-
 // ::timespec_get is provided by the C library, but it's marked as
 // unavailable until macOS 10.15
 // XFAIL: target={{.+}}-apple-macosx10.{{13|14}}