Adds a meta on top of every generated class to hide 'Edit on Github' link

Linked docs issue https://github.com/godotengine/godot-docs/pull/2656

(cherry picked from commit d83b8881ae15e156590dfe47b00e2e6059286e69)

doc/tools/makerst.py

@@ -343,6 +343,7 @@ def make_rst_class(class_def, state, dry_run, output_dir):  # type: (ClassDef, S
         f = open(os.path.join(output_dir, "class_" + class_name.lower() + '.rst'), 'w', encoding='utf-8')
 
     # Warn contributors not to edit this file directly
+    f.write(":github_url: hide\n\n")
     f.write(".. Generated automatically by doc/tools/makerst.py in Godot's source tree.\n")
     f.write(".. DO NOT EDIT THIS FILE, but the " + class_name + ".xml source instead.\n")
     f.write(".. The source is found in doc/classes or modules/<name>/doc_classes.\n\n")