Do not write messages from UpdatePullRequestState

[draftcode]

We want to use this method in other places. It should not write the
stderr to avoid interference with the output of the caller.

[aviator-app]

Current Aviator status

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Stack

1. 👉 Do not write messages from UpdatePullRequestState #284 👈 (this pr)

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[aviator-app]

FlexReview Summary

Based on the code complexity and the author's expertise score, these are the suggested reviewers:

• @jainankit (current review load: 3)

See the list of alternate reviewers in the detailed breakdown below.

Detailed Breakdown

Author’s expertise score for the modified files:

• internal/actions/pr.go (1.00)
• internal/actions/sync_branch.go (1.00)

Files	Reviewers
internal/actions/pr.go †, internal/actions/sync_branch.go †	@jainankit (score: 0.49, current review load: 3), @doratzeng (score: 0.08, current review load: 1)

† Indicates that the file doesn't need an expert review. (?)

See full breakdown of the reviewers on the Aviator webapp.

[aviator-app]

This PR is stacked on top of #283 which was merged. This PR (and its dependents) need to be synchronized on the commit that was merged into master. From your repository, run the following commands:

# Switch to this branch
git checkout extract_messages
# Sync this branch (and its children) on top of the merge commit
av stack sync
# Optionally update pull requests to match new stack
av stack submit