Remove plural bindings in GL_ARB_shader_texture_image_samples

It is not possible to have more than one texture per binding.

Fixes GitLab GLSL issue 80.

extensions/ARB/ARB_shader_texture_image_samples.txt

@@ -109,8 +109,7 @@ Modifications to The OpenGL Shading Language Specification, Version 4.40.08
 
     Description:
 
-        Returns the number of samples of the texture or textures bound to
-        <sampler>. 
+        Returns the number of samples of the texture bound to <sampler>.
 
 Add to table in section 8.12 "Image Functions"
 
@@ -121,7 +120,7 @@ Add to table in section 8.12 "Image Functions"
 
     Description:
 
-        Returns the number of samples of the image or images bound to <image>. 
+        Returns the number of samples of the image bound to <image>.
 
 Dependencies on ARB_shader_image_load_store and GLSL 4.20.