LibGL: Make glDeleteTextures skip over 0 names

As stated in the manual:
     glDeleteTextures silently ignores 0's and names that do not
     correspond to existing textures.

If we do not skip these 0 names, they end up as invalid free texture
names in our name allocator.

Userland/Libraries/LibGL/Tex/NameAllocator.h

@@ -16,7 +16,7 @@ public:
     TextureNameAllocator() = default;
 
     void allocate(GLsizei count, GLuint* textures);
-    void free(GLsizei count, const GLuint* textures);
+    void free(GLuint texture);
 
 private:
     Stack<GLuint, 512> m_free_texture_names;