Upgrade PR action to v3 (#3946)

Should fix usage https://github.com/google/iree/actions/runs/374897375
of disabled set-env and add-path commands.
diff --git a/.github/workflows/update_llvm_dependent_submodules.yml b/.github/workflows/update_llvm_dependent_submodules.yml
index bd0319a..2d66b0a 100644
--- a/.github/workflows/update_llvm_dependent_submodules.yml
+++ b/.github/workflows/update_llvm_dependent_submodules.yml
@@ -42,7 +42,7 @@
           echo "TF_SHA=$(git submodule status third_party/tensorflow | awk '{print $1}' | cut -c -12)" >> $GITHUB_ENV
           echo "LLVM_BAZEL_SHA=$(git submodule status third_party/llvm-bazel | awk '{print $1}' | cut -c -12)" >> $GITHUB_ENV
       - name: Creating Pull Request
-        uses: peter-evans/create-pull-request@v2
+        uses: peter-evans/create-pull-request@v3
         with:
           # Personal token is required to trigger additional automation (e.g. presubmits).
           token: ${{ secrets.GITHUB_WRITE_ACCESS_TOKEN }}