try not upgrading pip for more determinism/security

Author: vszakats

.github/workflows/build.yml

@@ -73,7 +73,6 @@ jobs:
 
       - name: Install test dependencies
         run: |
-          python -m pip install --upgrade pip
           pip install '.[python-tests]'
 
       - name: Run TLV constants sync test

.github/workflows/pages-ci.yml

@@ -27,7 +27,6 @@ jobs:
 
       - name: Install dependencies
         run: |
-          python -m pip install --upgrade pip
           pip install '.[browser-tests]'
           python -m playwright install
 

.github/workflows/pages.yml

@@ -24,7 +24,6 @@ jobs:
 
       - name: Install dependencies
         run: |
-          python -m pip install --upgrade pip
           pip install '.[page-gen]'
 
       - name: Generate decoder HTML