doc: whoops, wrong extension name.

doc/opengl-support.dox

@@ -322,7 +322,7 @@ Extension                                   | Status
 @gl_extension{EXT,shader_integer_mix}       | done (shading language only)
 @gl_extension{EXT,debug_label}              | missing pipeline and sampler label
 @gl_extension{EXT,debug_marker}             | done
-@gl_extension{EXT,sRGB_R8}                  | done
+@gl_extension{EXT,texture_sRGB_R8}          | done
 @gl_extension{GREMEDY,string_marker}        | done
 @gl_extension{NV,sample_locations}          | |
 @gl_extension{NV,fragment_shader_barycentric} | done (shading language only)
@@ -470,8 +470,8 @@ Extension                                   | Status
 @gl_extension{EXT,texture_compression_s3tc} | done
 @gl_extension{EXT,pvrtc_sRGB}               | done
 @gl_extension{EXT,shader_integer_mix}       | done (shading language only)
-@gl_extension{EXT,sRGB_R8}                  | done
+@gl_extension{EXT,texture_sRGB_R8}          | done
-@gl_extension{EXT,sRGB_RG8}                 | done
+@gl_extension{EXT,texture_sRGB_RG8}         | done
 @gl_extension{EXT,polygon_offset_clamp}     | |
 @gl_extension{EXT,clip_cull_distance}       | done
 @gl_extension{EXT,texture_compression_rgtc} | done