Remove filter options

None of the filters used the options. The filter API version was already
incremented once for 2.3 so there's no need to increment it again.

examples/examplefilter.hh

@@ -26,7 +26,7 @@ public:
     ~ExampleFilter();
 
     // Creates a new filter instance
-    static ExampleFilter* create(const char* zName, char** pzOptions, MXS_CONFIG_PARAMETER* ppParams);
+    static ExampleFilter* create(const char* zName, MXS_CONFIG_PARAMETER* ppParams);
 
     // Creates a new session for this filter
     ExampleFilterSession* newSession(MXS_SESSION* pSession);