Drop support of the build option USE_GLOO_IBVERBS (#33163)

Summary:
Two releases have passed since its deprecation:
8a026d4f74b71944ac2860c315996165a40f5626
Pull Request resolved: https://github.com/pytorch/pytorch/pull/33163

Differential Revision: D19850713

Pulled By: ezyang

fbshipit-source-id: 30a60df470b88e8c40e33112296e437cde29c49f
diff --git a/tools/setup_helpers/cmake.py b/tools/setup_helpers/cmake.py
index 1708566..4f64709 100644
--- a/tools/setup_helpers/cmake.py
+++ b/tools/setup_helpers/cmake.py
@@ -218,7 +218,6 @@
             '_GLIBCXX_USE_CXX11_ABI': 'GLIBCXX_USE_CXX11_ABI',
             'CUDNN_LIB_DIR': 'CUDNN_LIBRARY',
             'USE_CUDA_STATIC_LINK': 'CAFFE2_STATIC_LINK_CUDA',
-            'USE_GLOO_IBVERBS': 'USE_IBVERBS'   # Backward compatibility. Will be removed in the future.
         }
         additional_options.update({
             # Build options that have the same environment variable name and CMake variable name and that do not start
@@ -246,9 +245,6 @@
              'WERROR')
         })
 
-        if 'USE_GLOO_IBVERBS' in my_env:
-            print("WARNING: USE_GLOO_IBVERBS is deprecated. Use USE_IBVERBS instead.")
-
         for var, val in my_env.items():
             # We currently pass over all environment variables that start with "BUILD_", "USE_", and "CMAKE_". This is
             # because we currently have no reliable way to get the list of all build options we have specified in