Drop support of Qt 5

Also remove usage of some deprecated stuff.

PR #19338.

.github/workflows/ci_macos.yaml

@@ -19,7 +19,7 @@ jobs:
       matrix:
         libt_version: ["2.0.9", "1.2.19"]
         qbt_gui: ["GUI=ON", "GUI=OFF"]
-        qt_version: ["5.15.2", "6.5.0"]
+        qt_version: ["6.5.0"]
         exclude:
           - libt_version: "1.2.19"
             qt_version: "6.5.0"
@@ -88,25 +88,6 @@ jobs:
           cmake --build build
           sudo cmake --install build
 
-      - name: Build qBittorrent (Qt5)
-        if: startsWith(matrix.qt_version, 5)
-        run: |
-          CXXFLAGS="$CXXFLAGS -Werror -Wno-error=deprecated-declarations" \
-          LDFLAGS="$LDFLAGS -gz" \
-          cmake \
-            -B build \
-            -G "Ninja" \
-            -DCMAKE_BUILD_TYPE=RelWithDebInfo \
-            -DCMAKE_EXPORT_COMPILE_COMMANDS=ON \
-            -DBOOST_ROOT="${{ env.boost_path }}" \
-            -DOPENSSL_ROOT_DIR="${{ env.openssl_root }}" \
-            -DTESTING=ON \
-            -DVERBOSE_CONFIGURE=ON \
-            -D${{ matrix.qbt_gui }}
-          cmake --build build --target qbt_update_translations
-          cmake --build build
-          cmake --build build --target check
-
       - name: Build qBittorrent (Qt6)
         if: startsWith(matrix.qt_version, 6)
         run: |
@@ -119,7 +100,6 @@ jobs:
             -DCMAKE_EXPORT_COMPILE_COMMANDS=ON \
             -DBOOST_ROOT="${{ env.boost_path }}" \
             -DOPENSSL_ROOT_DIR="${{ env.openssl_root }}" \
-            -DQT6=ON \
             -DTESTING=ON \
             -DVERBOSE_CONFIGURE=ON \
             -D${{ matrix.qbt_gui }}