Update dependencies on '6.4.0' in qt/qtlanguageserver

Change-Id: I24b0d8a8bdbda60d198c23e2dfb1eef4b81120fb
Reviewed-by: Qt Submodule Update Bot <qt_submodule_update_bot@qt-project.org>

dependencies.yaml

 dependencies:
   ../qtbase:
-    ref: ffa3c3579acaf3291b0cfa7e5670313d576d5d49
+    ref: b4586e0c050653359d992d14f9b7a3c9f546c0a1
     required: true