ci: bump pnpm/action-setup to v6.0.8

v6.0.3 carries a regression (pnpm/action-setup#225, learningequality#227) that ignores the
packageManager-pinned pnpm version and installs pnpm 11, which requires
Node.js >=22.13 and fails on our Node 20 runners. v6.0.7 restored self-update
to the packageManager-pinned version (10.33.0).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: rtibbles

.github/workflows/deploytest.yml

@@ -33,7 +33,7 @@ jobs:
     steps:
     - uses: actions/checkout@v6
     - name: Use pnpm
-      uses: pnpm/action-setup@v6.0.3
+      uses: pnpm/action-setup@v6.0.8
     - name: Use Node.js
       uses: actions/setup-node@v6
       with:
@@ -63,7 +63,7 @@ jobs:
         # Use uv to install dependencies directly from requirements files
         uv pip sync requirements.txt
     - name: Use pnpm
-      uses: pnpm/action-setup@v6.0.3
+      uses: pnpm/action-setup@v6.0.8
     - name: Use Node.js
       uses: actions/setup-node@v6
       with:

.github/workflows/frontendtest.yml

@@ -33,7 +33,7 @@ jobs:
     steps:
     - uses: actions/checkout@v6
     - name: Use pnpm
-      uses: pnpm/action-setup@v6.0.3
+      uses: pnpm/action-setup@v6.0.8
     - name: Use Node.js
       uses: actions/setup-node@v6
       with:

.github/workflows/i18n-download.yml

@@ -25,7 +25,7 @@ jobs:
         run: uv pip sync requirements.txt
 
       - name: Use pnpm
-        uses: pnpm/action-setup@v6.0.3
+        uses: pnpm/action-setup@v6.0.8
 
       - name: Use Node.js
         uses: actions/setup-node@v6

.github/workflows/i18n-upload.yml

@@ -25,7 +25,7 @@ jobs:
         run: uv pip sync requirements.txt
 
       - name: Use pnpm
-        uses: pnpm/action-setup@v6.0.3
+        uses: pnpm/action-setup@v6.0.8
 
       - name: Use Node.js
         uses: actions/setup-node@v6

.github/workflows/pre-commit.yml

@@ -41,7 +41,7 @@ jobs:
         python-version: '3.10'
         ignore-nothing-to-cache: 'true'
     - name: Use pnpm
-      uses: pnpm/action-setup@v6.0.3
+      uses: pnpm/action-setup@v6.0.8
     - name: Use Node.js
       uses: actions/setup-node@v6
       with: