Revert "really switch to qmake automatically if pkg-config fails"

This reverts commit 0045d95a16.

<jeandet> nirbheek, it seems 0045d95a16 is
really wrong, I've tested on Ubuntu.  While writing this line I was
thinking that you can't have Qt without a working qmake in the path. On
Ubuntu you have that qtchooser stuff which is misleading.

mesonbuild/dependencies/ui.py

@@ -215,7 +215,7 @@ class QtBaseDependency(ExternalDependency):
         if DependencyMethods.PKGCONFIG in self.methods:
             self._pkgconfig_detect(mods, kwargs)
             methods.append('pkgconfig')
-        if not self.is_found or DependencyMethods.QMAKE in self.methods:
+        if not self.is_found and DependencyMethods.QMAKE in self.methods:
             from_text = self._qmake_detect(mods, kwargs)
             methods.append('qmake-' + self.name)
             methods.append('qmake')