qbs build: Remove code for creating deployment packages

Not a use case anymore, and if it were, we'd do it using built-in
capabilities.

Change-Id: I4c588ad7fb282530880210cb4c5795677074b1e0
Reviewed-by: Christian Stenger <christian.stenger@qt.io>

src/libs/cplusplus/cplusplus.qbs

@@ -3,12 +3,6 @@ import qbs 1.0
 Project {
     name: "CPlusPlus"
 
-    QtcDevHeaders { }
-    QtcDevHeaders {
-        productName: "cplusplus (3rd party)"
-        baseDir: sourceDirectory + "/../3rdparty/cplusplus"
-    }
-
     QtcLibrary {
         cpp.includePaths: base.concat("../3rdparty")
         cpp.defines: base.concat([