chore: set a fixed pnpm version in builder image (#391)

Signed-off-by: Philippe Martin <phmartin@redhat.com>

Author: feloy

build/Containerfile.builder

@@ -29,5 +29,5 @@ COPY tests/playwright/package.json tests/playwright/package.json
 COPY .npmrc .npmrc
 
 RUN npm i -g ssh2@1.16.0 && \
-    npm install --global pnpm@10 && \
+    npm install --global pnpm@10.20.0 && \
     pnpm --frozen-lockfile install