C++: Correct src/libs/cplusplus dependencies

There is no dependency to languageutils, but we now depend on cplusplus
since we use/call Utils::FileName and Utils::FileDropSupport.

Change-Id: I18ca659ec3023a146e9e358e33dabbf9805fb6ce
Reviewed-by: Orgad Shaneh <orgads@gmail.com>

src/libs/cplusplus/cplusplus_dependencies.pri

 QTC_LIB_NAME = CPlusPlus
 QTC_LIB_DEPENDS += \
-    languageutils
+    utils
 INCLUDEPATH *= $$IDE_SOURCE_TREE/src/libs/3rdparty