Scratchpad: Use QAbstractItemView::clicked instead of activated

The behavior for QAbstractItemView::activated is inconsistent
across different platforms and may make it unintuitive.
1 job for !41 with scratchpad-fix in 60 minutes (queued for 2 seconds)
latest detached
Status Job ID Name Coverage
  Build
failed #13669
linux kf5-qt5 qt5.12

01:00:00

 
Name Stage Failure
failed
linux kf5-qt5 qt5.12 Build The script exceeded the maximum execution time set for the job
        Start  75: test_lldbformatters
kf5.kinit.klauncher: new app ":1.41"
kf5.kinit.klauncher: new app "org.kdevelop.kdevplatform-lock-7c35227d-7c45-464d-a222-4280c3195241"
75/121 Test #75: test_lldbformatters ..................... Passed 29.25 sec
Start 76: test_gdb
kf5.kinit.klauncher: new app ":1.42"
kf5.kinit.klauncher: new app "org.kdevelop.kdevplatform-lock-5edd2069-aa6f-4f30-bc63-efb577cf93ab"
Pulling docker image gitlab/gitlab-runner-helper:x86_64-ac2a293c ...
ERROR: Job failed: execution took longer than 1h0m0s seconds