VCS polishing: Change context menu entry for 'Blame parent'.

... for git, hg as it is not obvious from the SHA1 displayed.

src/plugins/mercurial/mercurialeditor.cpp

@@ -55,6 +55,7 @@ MercurialEditor::MercurialEditor(const VCSBase::VCSBaseEditorParameters *type, Q
         diffIdentifier(QLatin1String(Constants::DIFFIDENTIFIER))
 {
     setAnnotateRevisionTextFormat(tr("Annotate %1"));
+    setAnnotatePreviousRevisionTextFormat(tr("Annotate parent revision %1"));
 }
 
 QSet<QString> MercurialEditor::annotationChanges() const