fix: remove all pnpm version specifications from CI workflow

The pnpm/action-setup@v4 action automatically detects the version from
package.json's packageManager field. Specifying version: 9 causes conflicts.

Author: aaronlippold

.github/workflows/ci.yml

@@ -35,8 +35,6 @@ jobs:
 
       - name: Install pnpm
         uses: pnpm/action-setup@v4
-        with:
-          version: 9
 
       - uses: actions/setup-node@v4
         with:
@@ -59,8 +57,6 @@ jobs:
 
       - name: Install pnpm
         uses: pnpm/action-setup@v4
-        with:
-          version: 9
 
       - uses: actions/setup-node@v4
         with:
@@ -83,8 +79,6 @@ jobs:
 
       - name: Install pnpm
         uses: pnpm/action-setup@v4
-        with:
-          version: 9
 
       - uses: actions/setup-node@v4
         with:
@@ -95,4 +89,4 @@ jobs:
         run: pnpm install --frozen-lockfile
 
       - name: Security audit
-        run: pnpm audit
+        run: pnpm audit