mark packages-autoroller bringup again (#129859)

Even after updating the account (and the cloudKMS GitHub token), when
the bot tries to push to
https://github.com/flutter-pub-roller-bot/flutter, it gets a 403, which
probably means authentication failed. I will have to investigate next
week.

```
Exception: GitException: Exception on command "push https://[GitHub TOKEN]@github.com/flutter-pub-roller-bot/flutter.git packages-autoroller-branch-1:packages-autoroller-branch-1": Command "git push https://[GitHub TOKEN]@github.com/flutter-pub-roller-bot/flutter.git packages-autoroller-branch-1:packages-autoroller-branch-1" failed in directory "/b/s/w/ir/x/w/flutter_conductor_checkouts/framework" to update the release branch with the commit. Git exited with error code 128.
stderr from git:
16:33:21.199510 exec-cmd.c:90           trace: resolved executable path from procfs: /b/s/w/ir/cipd_bin_packages/bin/git
16:33:21.199587 exec-cmd.c:237          trace: resolved executable dir: /b/s/w/ir/cipd_bin_packages/bin
16:33:21.200155 git.c:460               trace: built-in: git push https://[GitHub TOKEN]@github.com/flutter-pub-roller-bot/flutter.git packages-autoroller-branch-1:packages-autoroller-branch-1
16:33:21.200542 run-command.c:655       trace: run_command: GIT_DIR=.git git remote-https https://[GitHub TOKEN]@github.com/flutter-pub-roller-bot/flutter.git https://[GitHub TOKEN]@github.com/flutter-pub-roller-bot/flutter.git
16:33:21.201787 exec-cmd.c:90           trace: resolved executable path from procfs: /b/s/w/ir/cipd_bin_packages/libexec/git-core/git
16:33:21.201845 exec-cmd.c:237          trace: resolved executable dir: /b/s/w/ir/cipd_bin_packages/libexec/git-core
16:33:21.202175 git.c:750               trace: exec: git-remote-https https://[GitHub TOKEN]@github.com/flutter-pub-roller-bot/flutter.git https://[GitHub TOKEN]@github.com/flutter-pub-roller-bot/flutter.git
16:33:21.202195 run-command.c:655       trace: run_command: git-remote-https https://[GitHub TOKEN]@github.com/flutter-pub-roller-bot/flutter.git https://[GitHub TOKEN]@github.com/flutter-pub-roller-bot/flutter.git
16:33:21.203510 exec-cmd.c:90           trace: resolved executable path from procfs: /b/s/w/ir/cipd_bin_packages/libexec/git-core/git-remote-http
16:33:21.203567 exec-cmd.c:237          trace: resolved executable dir: /b/s/w/ir/cipd_bin_packages/libexec/git-core
remote: Permission to flutter-pub-roller-bot/flutter.git denied to flutter-pub-roller-bot.
fatal: unable to access 'https://github.com/flutter-pub-roller-bot/flutter.git/': The requested URL returned error: 403
```


https://ci.chromium.org/ui/p/flutter/builders/prod/Linux%20packages_autoroller/6031/overview

This is still being tracked in
https://github.com/flutter/flutter/issues/129744

.ci.yaml

@@ -243,6 +243,8 @@ targets:
 
   - name: Linux packages_autoroller
     presubmit: false
+    # TODO(fujino): https://github.com/flutter/flutter/issues/129744
+    bringup: true
     recipe: pub_autoroller/pub_autoroller
     timeout: 30
     enabled_branches: