Add r: timeout label to bugs/pr closed by no response bot. (#129408)

Adds r: timeout to bugs closed by inactivity.

Bug: https://github.com/flutter/flutter/issues/104962

.github/workflows/no-response.yaml

@@ -36,6 +36,7 @@ jobs:
           # Number of days of inactivity before an issue is closed for lack of response.
           days-before-stale: -1
           days-before-close: 21
+          close-issue-label: "r: timeout"
           # Label requiring a response.
           stale-issue-label: "waiting for customer response"
           stale-pr-label: "needs-info"
@@ -43,3 +44,4 @@ jobs:
             Without additional information we're not able to resolve this PR.
             Feel free to add more info or respond to any questions above.
             Thanks for your contribution!
+          close-pr-label: "r: timeout"