Add clearing of `static_gdscript_cache` to `GDScriptCache`

(cherry picked from commit db5e843e468b7a69aeaebdf1e4159d2741b660fd)

modules/gdscript/gdscript_cache.cpp

@@ -485,6 +485,7 @@ void GDScriptCache::clear() {
 	parser_map_refs.clear();
 	singleton->shallow_gdscript_cache.clear();
 	singleton->full_gdscript_cache.clear();
+	singleton->static_gdscript_cache.clear();
 }
 
 GDScriptCache::GDScriptCache() {