Fix modulemap linting

Author: ldionne

libcxx/test/libcxx/lint/lint_headers.sh.py

@@ -11,7 +11,7 @@
 def exclude_from_consideration(path):
     return (
         path.endswith(".txt")
-        or path.endswith(".modulemap.in")
+        or path.endswith(".modulemap")
         or os.path.basename(path) == "__config"
         or os.path.basename(path) == "__config_site.in"
         or os.path.basename(path) == "libcxx.imp"