updated Qt in CI to 6.6.0 and removed commercial-only LTS Qt versions (#5561)

Updates for the Qt 6.2.x and 6.5.x LTS versions are only being provided
to commercial customers so the latest version is the only feasible one
to use.

Builds with older 6.x versions are still being tested implicitly by
using the Qt versions provided by the various distros.

.github/workflows/CI-windows.yml

@@ -28,7 +28,7 @@ jobs:
     strategy:
       matrix:
         os: [windows-2019, windows-2022]
-        qt_ver: [5.15.2, 6.2.4, 6.5.3]
+        qt_ver: [5.15.2, 6.6.0]
       fail-fast: false
 
     runs-on: ${{ matrix.os }}

.github/workflows/clang-tidy.yml

@@ -20,7 +20,7 @@ jobs:
     runs-on: ubuntu-22.04
 
     env:
-      QT_VERSION: 6.5.3
+      QT_VERSION: 6.6.0
 
     steps:
       - uses: actions/checkout@v3

.github/workflows/selfcheck.yml

@@ -20,7 +20,7 @@ jobs:
     runs-on: ubuntu-22.04
 
     env:
-      QT_VERSION: 6.5.3
+      QT_VERSION: 6.6.0
 
     steps:
       - uses: actions/checkout@v3