Revert "Cleanup: GPU: Reduce compilation warnings"

This reverts commit 3ca5f6f62e.

There were some performance regressions detected.

Fixes: #135215, #134941

source/blender/gpu/shaders/common/gpu_shader_math_vector_lib.glsl

@@ -16,12 +16,9 @@
 /**
  * Return true if all components is equal to zero.
  */
-#    pragma GCC diagnostic push
-#    pragma GCC diagnostic ignored "-Wredundant-decls"
 bool is_zero(vec2 vec);
 bool is_zero(vec3 vec);
 bool is_zero(vec4 vec);
-#    pragma GCC diagnostic pop * /
 
 /**
  * Return true if any component is equal to zero.