qbs build: Remove workarounds for fixed qbs bug.

That was most likely QBS-755.

Change-Id: I43d0316113fcca79554bfee9eee9b8bd706fce07
Reviewed-by: Joerg Bornemann <joerg.bornemann@theqtcompany.com>

tests/auto/utils/stringutils/stringutils.qbs

@@ -3,6 +3,5 @@ import qbs
 QtcAutotest {
     name: "StringUtils autotest"
     Depends { name: "Utils" }
-    Depends { name: "Qt.widgets" } // TODO: Remove when qbs bug is fixed
     files: "tst_stringutils.cpp"
 }