Raise GIT_HTTP_LOW_SPEED_TIME to 300 for CI

Turns out 60 seconds is not always enough for a build (since during the build, there are no transfers obviously, so it kicks in together with GIT_HTTP_LOW_SPEED_LIMIT=1000)

Author: dzuelke

.github/workflows/ci.yml

@@ -23,7 +23,7 @@ env:
   HEROKU_API_KEY: ${{ secrets.HEROKU_API_KEY }}
   HEROKU_API_USER: ${{ secrets.HEROKU_API_USER }}
   GIT_HTTP_LOW_SPEED_LIMIT: 1000
-  GIT_HTTP_LOW_SPEED_TIME: 60
+  GIT_HTTP_LOW_SPEED_TIME: 300
 
 jobs:
   integration-test: