Fix-references-to-raw-github-content (cyberbotics#6667)

* Replace reference to raw github content with webots:// in ShapeWithFixedWebTexture.proto.

The reference to a file in the github develop branch was causing that file to be left as changed when running test_suite.py in the develop branch.

tests/cache/protos/ShapeWithFixedWebTexture.proto

@@ -8,7 +8,7 @@ PROTO ShapeWithFixedWebTexture [
     appearance PBRAppearance {
       baseColorMap ImageTexture {
         url [
-          "https://raw.githubusercontent.com/cyberbotics/webots/develop/tests/cache/protos/textures/blue_texture.jpg"
+          "webots://tests/cache/protos/textures/blue_texture.jpg"
         ]
       }
     }