.github/workflows: reviewing depaware.txt is unnecessary (#16989)

@tailscale/dataplane almost never needs to review depaware.txt, when
it is the only change to the DERP implementation.

Related #16372
Updates #cleanup

Signed-off-by: Simon Law <sfllaw@tailscale.com>

.github/workflows/request-dataplane-review.yml

@@ -8,6 +8,8 @@ on:
       - ".github/workflows/request-dataplane-review.yml"
       - "**/*derp*"
       - "**/derp*/**"
+    paths-ignore:
+      - "**/depaware.txt"
 
 jobs:
   request-dataplane-review: