Complete the truncated channel shutdown comment in UpstreamGrpcSenderProvider

[thswlsqls]

No issue: trivial comment fix, PR-only per contribution policy.

Description

• The comment on the fallback branch in UpstreamGrpcSenderProvider#createSender ends mid-sentence at "if", so it never states the condition. It has been truncated since Use minimal fallback managed channel when none is specified #6110 (da7796b3b) added it — no full sentence ever existed, so this wording is newly written, not restored.
• The clause comes from the branch itself: this else runs when no ManagedChannel was configured, so the sender creates the fallback channel and owns it. shutdownChannel starts false, is set true only here, and is read only by UpstreamGrpcSender.shutdown() — it expresses channel ownership. Different wording is welcome.
• Comment-only; no behavior, signature, or public API change.

Testing done

• Comment-only, test-exempt: no test added.
• ./gradlew :exporters:sender:grpc-managed-channel:check — BUILD SUCCESSFUL, 3 tests passed (UpstreamGrpcSenderTest); includes spotless, ErrorProne/NullAway, and jApiCmp.
• docs/apidiffs/current_vs_latest/opentelemetry-exporter-sender-grpc-managed-channel.txt still reads No changes., so no apidiff was staged.
• Integration (*IT) and GraalVM native-image tests were not run locally.

[opentelemetry-pr-dashboard]

Pull request dashboard status

Waiting on reviewers · refreshed 2026-09-02 14:35 UTC

Review the latest changes.

Status above doesn't look right?

• Just replied or pushed? Anything around or after the refresh time above may not be picked up yet — give it a few minutes.
• Anything look wrong? Report it with what you expected; it helps us improve the dashboard.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 91.29%. Comparing base (e2efec5) to head (be7f0fe).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff            @@
##               main    #8753   +/-   ##
=========================================
  Coverage     91.29%   91.29%           
- Complexity    10498    10500    +2     
=========================================
  Files          1006     1006           
  Lines         28338    28338           
  Branches       3581     3581           
=========================================
+ Hits          25870    25872    +2     
  Misses         1675     1675           
+ Partials        793      791    -2     

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.