Drop keep-hash fro docs PR builds

.buildkite/scripts/build_pr.sh

@@ -54,7 +54,8 @@ if [[ "${GITHUB_PR_BASE_REPO}" != 'docs' ]]; then
       git fetch origin pull/$GITHUB_PR_NUMBER/head:$GITHUB_PR_BRANCH &&
       git switch $GITHUB_PR_BRANCH &&
       cd ..
-
+  # For product repos - context in https://github.com/elastic/docs/commit/5b06c2dc1f50208fcf6025eaed6d5c4e81200330
+  build_args+=" --keep_hash"
   build_args+=" --sub_dir $GITHUB_PR_BASE_REPO:$GITHUB_PR_TARGET_BRANCH:./product-repo"
 else
   # Buildkite PR bot for the `elastic/docs` repo is configured to checkout the PR directly into the workspace
@@ -72,7 +73,7 @@ fi
 TARGET_BRANCH="${GITHUB_PR_BASE_REPO}_bk_${GITHUB_PR_NUMBER}"
 PREVIEW_URL="https://${TARGET_BRANCH}.docs-preview.app.elstc.co"
 
-build_cmd="./build_docs --all --keep_hash \
+build_cmd="./build_docs --all \
   --target_repo [email protected]:elastic/built-docs \
   --reference /opt/git-mirrors/ \
   --target_branch ${TARGET_BRANCH} \