Update dependencies on '6.4' in qt/qtlanguageserver

Change-Id: Ie88598087ba6f05919ba88728e7f5a07e3e57c26
Reviewed-by: Qt Submodule Update Bot <qt_submodule_update_bot@qt-project.org>

dependencies.yaml

 dependencies:
   ../qtbase:
-    ref: 30e09fce19fb3aaed9be22d6f0ec3284c8c50391
+    ref: 518118991f0ab96e4764b65a59b5db2f89e75f42
     required: true