Rename godot_shader_language_style_guide, shorten title

Closes #4159

tutorials/shading/index.rst

@@ -12,7 +12,7 @@ Shading
    intro_to_shaders_water_workshop
    screen-reading_shaders
    migrating_to_godot_shader_language
-   godot_shader_language_style_guide
+   shaders_style_guide
    advanced_postprocessing
    using_viewport_as_texture
    custom_postprocessing

tutorials/shading/godot_shader_language_style_guide.rst → tutorials/shading/shaders_style_guide.rst

@@ -1,7 +1,7 @@
-.. _doc_godot_shader_language_style_guide:
+.. _doc_shaders_style_guide:
 
-Godot shader language style guide
-=================================
+Shaders style guide
+===================
 
 This style guide lists conventions to write elegant shaders. The goal is to
 encourage writing clean, readable code and promote consistency across projects,