Drop QT_MAJOR_VERSION

PKGBUILD

@@ -29,8 +29,7 @@ validpgpkeys=(CA262C6C83DE4D2FB28A332A3A6A4DB839EAA6D7  # Albert Astals Cid <aac
 build() {
   cmake -B build -S $pkgname-$pkgver \
     -DBUILD_TESTING=OFF \
-    -DBUILD_QCH=ON \
-    -DQT_MAJOR_VERSION=6
+    -DBUILD_QCH=ON
   cmake --build build
 }