ci: Remove mentions of conda-forge for Python 3.9 (#1597)

No longer needed for Python 3.9
Signed-off-by: Eli Uriegas <eliuriegas@fb.com>

.circleci/config.yml

@@ -52,9 +52,7 @@ commands:
           name: Adding CONDA_CHANNEL_FLAGS to BASH_ENV
           command: |
               CONDA_CHANNEL_FLAGS=""
-              if [[ "${PYTHON_VERSION}" = *3.9* ]]; then
-                echo "export CONDA_CHANNEL_FLAGS=-c=conda-forge" >> ${BASH_ENV}
-              fi
+              # formerly used to add conda-forge flags for Python 3.9, reserving the mechanism for future python upgrades
 
 binary_common: &binary_common
   parameters:

.circleci/config.yml.in

@@ -52,9 +52,7 @@ commands:
           name: Adding CONDA_CHANNEL_FLAGS to BASH_ENV
           command: |
               CONDA_CHANNEL_FLAGS=""
-              if [[ "${PYTHON_VERSION}" = *3.9* ]]; then
-                echo "export CONDA_CHANNEL_FLAGS=-c=conda-forge" >> ${BASH_ENV}
-              fi
+              # formerly used to add conda-forge flags for Python 3.9, reserving the mechanism for future python upgrades
 
 binary_common: &binary_common
   parameters:

.circleci/torchscript_bc_test/environment.yml

 channels:
-  - conda-forge
   - defaults
 dependencies:
   - flake8

.circleci/unittest/windows/scripts/environment.yml

 channels:
-  - conda-forge
   - defaults
 dependencies:
   - flake8

packaging/pkg_helpers.bash

@@ -231,10 +231,6 @@ setup_conda_pytorch_constraint() {
   else
     export CONDA_CHANNEL_FLAGS="${CONDA_CHANNEL_FLAGS} -c pytorch -c pytorch-test -c pytorch-nightly"
   fi
-  # Some dependencies for Python 3.9 are only on conda-forge
-  if [[ "${PYTHON_VERSION}" = "3.9" ]]; then
-    export CONDA_CHANNEL_FLAGS="${CONDA_CHANNEL_FLAGS} -c conda-forge"
-  fi
   if [[ "$CU_VERSION" == cpu ]]; then
     export CONDA_PYTORCH_BUILD_CONSTRAINT="- pytorch==$PYTORCH_VERSION${PYTORCH_VERSION_SUFFIX}"
     export CONDA_PYTORCH_CONSTRAINT="- pytorch==$PYTORCH_VERSION"