Remove extra semi colon from oomd/util/PluginArgParser.cpp

Summary:
`-Wextra-semi` or `-Wextra-semi-stmt`

If the code compiles, this is safe to land.

Reviewed By: lnyng

Differential Revision: D52969146

fbshipit-source-id: 9c43d6ff0e051dc282c6314ca64e2df82f81f695

src/oomd/util/PluginArgParser.cpp

@@ -99,7 +99,7 @@ std::unordered_set<std::string> PluginArgParser::validArgNames() {
     res.emplace(entry.first);
   }
   return res;
-};
+}
 
 template <>
 int64_t PluginArgParser::parseValue(const std::string& valueString) {