Add permission to post the terraform plan in a comment (#2733)

After [restricting the id-token
permission](https://github.com/bazelbuild/continuous-integration/pull/2679/changes)
to the "detect-changes" steponly, it was stripped off any other general
permissions like: "pull-requests: write" (which was defined at the top
of the workflow)

We need to re-add it to this step to be able to post a comment with the
plan

.github/workflows/terraform.yml

diff --git a/.github/workflows/terraform.yml b/.github/workflows/terraform.yml
index febe9a0..d43d00e 100644
--- a/.github/workflows/terraform.yml
+++ b/.github/workflows/terraform.yml
@@ -66,6 +66,8 @@
     permissions:
       contents: read
       id-token: write
+      pull-requests: write
+      issues: write
 
     # Lock per organization. Cancels old runs on PRs (saves time), but queues pushes (safe apply).
     concurrency: