Make coverage token available in forks (#5479)

This fixes coverage submission in CI, which has been failing for PRs
submitted from forks.

Author: snejus

.github/workflows/ci.yaml

@@ -1,6 +1,6 @@
 name: Test
 on:
-  pull_request:
+  pull_request_target:
   push:
     branches:
       - master

.github/workflows/lint.yml

@@ -1,7 +1,7 @@
 name: Lint check
 run-name: Lint code
 on:
-  pull_request:
+  pull_request_target:
   push:
     branches:
       - master