[profile] Update a warning message (NFC)

It's possible for a merge pool specifier to appear anywhere in a
filename pattern. Update the warning to reflect this.

llvm-svn: 272685
diff --git a/compiler-rt/lib/profile/InstrProfilingFile.c b/compiler-rt/lib/profile/InstrProfilingFile.c
index a7ec7a0..1bd6c63 100644
--- a/compiler-rt/lib/profile/InstrProfilingFile.c
+++ b/compiler-rt/lib/profile/InstrProfilingFile.c
@@ -288,9 +288,8 @@
           }
       } else if (containsMergeSpecifier(FilenamePat, I)) {
         if (MergingEnabled) {
-          PROF_WARN(
-              "%%m specifier can only be specified once at the end of %s.\n",
-              FilenamePat);
+          PROF_WARN("%%m specifier can only be specified once in %s.\n",
+                    FilenamePat);
           return -1;
         }
         MergingEnabled = 1;