Fix project main scene path in Pong demos (#1217)

Signed-off-by: Sebastian Javier D'Alessandro Szymanowski <[email protected]>

2d/pong/project.godot

@@ -14,7 +14,7 @@ config/name="Pong with GDScript"
 config/description="A simple Pong game. This demo shows best practices
 for game development in Godot, including signals."
 config/tags=PackedStringArray("2d", "demo", "official")
-run/main_scene="pong.tscn"
+run/main_scene="res://pong.tscn"
 config/features=PackedStringArray("4.4")
 config/icon="res://icon.webp"
 

mono/pong/project.godot

@@ -14,7 +14,7 @@ config/name="Pong with C#"
 config/description="A simple Pong game. This demo shows best practices
 for game development in Godot, including signals."
 config/tags=PackedStringArray("2d", "demo", "official")
-run/main_scene="pong.tscn"
+run/main_scene="res://pong.tscn"
 config/features=PackedStringArray("4.4")
 config/icon="res://icon.webp"