QmlDebug: Remove redundant dependency from qbs file.

Change-Id: I2d3fd1286f185bff5eb5374d411087fad15a9568
Reviewed-by: Joerg Bornemann <joerg.bornemann@digia.com>

src/libs/qmldebug/qmldebug.qbs

@@ -6,7 +6,6 @@ QtcLibrary {
 
     cpp.defines: base.concat("QMLDEBUG_LIB")
 
-    Depends { name: "cpp" }
     Depends { name: "Qt"; submodules: ["gui", "network"] }
 
     files: [