fix: Flaky tests when run in GitHub Actions Workflow (#733)

## Description

Hey everyone! I initially attempted to resolve this issue by following
the approach mentioned in [this
issue](dart-lang/pub#3998) by setting the
environment variable `PUB_SUMMARY_ONLY=1` in the workflow. However, this
did not work as expected.

Then, I decided to solve it by updating the `ignoringDependencyMessages`
method in the matcher file, and this approach seems to be working fine.

**Changes:**

- Remove unnecessary TODO comment in the workflow file
- Update test command in workflow to remove unnecessary `|| true`
- Update dependency messages matcher in `matchers.dart` test file

Issue: #724

## Type of Change

- [ ] ✨ `feat` -- New feature (non-breaking change which adds
functionality)
- [x] 🛠️ `fix` -- Bug fix (non-breaking change which fixes an issue)
- [ ] ❌ `!` -- Breaking change (fix or feature that would cause existing
functionality to change)
- [ ] 🧹 `refactor` -- Code refactor
- [x] ✅ `ci` -- Build configuration change
- [ ] 📝 `docs` -- Documentation
- [ ] 🗑️ `chore` -- Chore

Author: jessicatarra

.github/workflows/validate.yaml

@@ -94,8 +94,7 @@ jobs:
       - name: Install Tools
         run: ./.github/workflows/scripts/install-tools.sh
       - name: Run Tests
-        # TODO: Remove | true once #724 iw solved.
-        run: melos test --no-select || true
+        run: melos test --no-select
 
   test_windows:
     runs-on: windows-latest

packages/melos/test/matchers.dart

@@ -20,6 +20,7 @@ Matcher ignoringDependencyMessages(String expected) {
           .where(
             (line) =>
                 !line.startsWith('Resolving dependencies...') &&
+                !line.startsWith('Downloading packages...') &&
                 !line.startsWith('Got dependencies!'),
           )
           .join('\n');