Fix: GPU: Reduce GPU_MAX_ATTR from 15 to 14

This is to accommodate Position and Normal attributes.
The normal used to be optional but isn't nowadays.

So the limit is actually 14 attributes until we do some big refactoring of
the attribute fetching.

Pull Request: https://projects.blender.org/blender/blender/pulls/118441

source/blender/gpu/GPU_shader.h

@@ -23,9 +23,9 @@ typedef struct GPUShaderCreateInfo GPUShaderCreateInfo;
 /** Opaque type hiding #blender::gpu::Shader */
 typedef struct GPUShader GPUShader;
 
-/* Hardware limit is 16. Position attribute is always needed so we reduce to 15.
+/* Hardware limit is 16. Position and Normal attributes are always needed, so we reduce them to 14.
  * This makes sure the GPUVertexFormat name buffer does not overflow. */
-#define GPU_MAX_ATTR 15
+#define GPU_MAX_ATTR 14
 
 /* Determined by the maximum uniform buffer size divided by chunk size. */
 #define GPU_MAX_UNIFORM_ATTR 8