[GTK4] Fix Test*Shell.test_setSizeCustomResize test failure

[akurtakov]

Translating coordinates from client area to GtkWindow for Gtk 4.x made the wrong assumption that it should reduce allocation.height with the offset (header/titlebar height) which makes no sense as it shrinks the window vertically.

[github-actions]

Test Results

   88 files   - 30     88 suites   - 30   8m 10s ⏱️ - 3m 37s
4 546 tests  - 37  4 512 ✅  - 35  34 💤  - 2  0 ❌ ±0 
  261 runs   - 69    239 ✅  - 68  22 💤  - 1  0 ❌ ±0 

Results for commit 75d80f2. ± Comparison against base commit 99aff36.

This pull request removes 37 tests.

AllGTKTests Test_GtkConverter ‑ test_HeuristicASCII_dollarSign
AllGTKTests Test_GtkConverter ‑ test_HeuristicASCII_emptyString
AllGTKTests Test_GtkConverter ‑ test_HeuristicASCII_letterA
AllGTKTests Test_GtkConverter ‑ test_HeuristicASCII_letters
AllGTKTests Test_GtkConverter ‑ test_HeuristicUTF16LE_null
AllGTKTests Test_GtkConverter ‑ test_HeuristicUTF16_AsciiLetters
AllGTKTests Test_GtkConverter ‑ test_HeuristicUTF16_Asciiletter
AllGTKTests Test_GtkConverter ‑ test_HeuristicUTF16_LotsOfLetters
AllGTKTests Test_GtkConverter ‑ test_HeuristicUTF16_letter
AllGTKTests Test_GtkConverter ‑ test_HeuristicUTF16_letters
…

♻️ This comment has been updated with latest results.

[jonahgraham]

I see the test failure is a Clipboard related test. I'll create a PR/issue for that soon.

[akurtakov]

Merging as it's actually reducing the failures on GTK 4.