Update GDScript submodule URL following extension repository transfer (…

…#1225)

Hi there! @grndctrl, the original author of the Godot/GDScript language
support extension, transferred the repository. I'll be the new
maintainer moving forward. This PR updates the submodule path to match
the new repository location. Please let me know if you need me to do
anything else. Thanks!

.gitmodules

@@ -284,7 +284,7 @@
 
 [submodule "extensions/gdscript"]
 	path = extensions/gdscript
-	url = https://github.com/grndctrl/zed-gdscript.git
+	url = https://github.com/GDQuest/zed-gdscript.git
 
 [submodule "extensions/gemini"]
 	path = extensions/gemini