.travis.yml: reenable PPA build on tag push (#26873)

Author: fjl

.travis.yml

@@ -140,7 +140,7 @@ jobs:
 
     # This builder does the Ubuntu PPA nightly uploads
     - stage: build
-      if: type = cron
+      if: type = cron || (type = push && tag ~= /^v[0-9]/)
       os: linux
       dist: bionic
       go: 1.20.x