ci: upgrade pip to avoid 21.3

As documented in:
  - tpm2-software#247

pip 21.3 was broken with in-place (-e) installs and was fixed in pip
21.3.1. However, the CI is still stuck on pip 21.3 and thus is broken.
When patch 57428, which pins pip to a version lower than 21.3 was
reverted, we need something to get us after 21.3, so update pip.

Signed-off-by: William Roberts <william.c.roberts@intel.com>

.github/workflows/tests.yaml

@@ -22,7 +22,9 @@ jobs:
       - name: Install dependencies
         env:
           TPM2_TSS_VERSION: ${{ matrix.tss-version }}
-        run: ./.ci/install-deps.sh
+        run: |
+          python3 -m pip install --user --upgrade pip>21.3
+          ./.ci/install-deps.sh
 
       - name: Check
         env: