Pin pip==21.2.4 everywhere (flyteorg#696)

Signed-off-by: Eduardo Apolinario <eapolinario@users.noreply.github.com>

Co-authored-by: Eduardo Apolinario <eapolinario@users.noreply.github.com>

.github/workflows/pythonbuild.yml

@@ -31,7 +31,7 @@ jobs:
         key: ${{ format('{0}-pip-{1}', runner.os, hashFiles('dev-requirements.txt', format('requirements{0}.txt', matrix.spark-version-suffix))) }}
     - name: Install dependencies
       run: |
-        python -m pip install --upgrade pip setuptools wheel
+        python -m pip install --upgrade pip==21.2.4 setuptools wheel
         make setup${{ matrix.spark-version-suffix }}
         pip freeze
     - name: Test with coverage
@@ -111,7 +111,7 @@ jobs:
             ${{ runner.os }}-pip-
       - name: Install dependencies
         run: |
-          python -m pip install --upgrade pip
+          python -m pip install --upgrade pip==21.2.4
           pip install -r dev-requirements.txt
       - name: Lint
         run: |
@@ -133,7 +133,7 @@ jobs:
           python-version: 3.8
       - name: Install dependencies
         run: |
-          python -m pip install --upgrade pip setuptools wheel
+          python -m pip install --upgrade pip==21.2.4 setuptools wheel
           pip install -r doc-requirements.txt
       - name: Build the documentation
         run: make -C docs html