docs: Put swr back on the GL_ARB_texture_buffer_object_rgb32 list.

Looks like this was lost when resolving merge conflicts in
commit d1fbd4cdb1bdb8041362a8e5f05833c43a39c9a6.
diff --git a/docs/GL3.txt b/docs/GL3.txt
index 6053d94..c185c69 100644
--- a/docs/GL3.txt
+++ b/docs/GL3.txt
@@ -128,7 +128,7 @@
   GL_ARB_sample_shading                                 DONE (i965/gen6+, nv50)
   GL_ARB_shader_subroutine                              DONE (i965/gen6+, nv50, llvmpipe, softpipe, swr)
   GL_ARB_tessellation_shader                            DONE (i965/gen7+)
-  GL_ARB_texture_buffer_object_rgb32                    DONE (i965/gen6+, llvmpipe, softpipe)
+  GL_ARB_texture_buffer_object_rgb32                    DONE (i965/gen6+, llvmpipe, softpipe, swr)
   GL_ARB_texture_cube_map_array                         DONE (i965/gen6+, nv50, llvmpipe, softpipe)
   GL_ARB_texture_gather                                 DONE (i965/gen6+, nv50, llvmpipe, softpipe, swr)
   GL_ARB_texture_query_lod                              DONE (i965, nv50, softpipe)