Remove leftover references to phutil_module_cache

Reviewed By: mzlee

Differential Revision: D5688624

fbshipit-source-id: c726b4e56bd823b994a7b713488fef93c6f796d0

.gitignore

@@ -39,7 +39,6 @@ coverage/COVERAGE_REPORT
 .gdbhistory
 .gdb_history
 package/
-.phutil_module_cache
 unity.a
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