Vcs: Drop VcsBaseOptionsPage hierarchy level

Adapt the remaining users: Cvs,Git,Svn.

Change-Id: Idd730a33e5c64d18002b1a21b5f5c715b7fa5ffb
Reviewed-by: Orgad Shaneh <orgads@gmail.com>

src/plugins/git/gitsettings.h

@@ -61,7 +61,7 @@ public:
 
     Utils::FilePath gitExecutable(bool *ok = nullptr, QString *errorMessage = nullptr) const;
 
-    GitSettings &operator = (const GitSettings &s);
+    GitSettings &operator=(const GitSettings &s) = default;
 };
 
 } // namespace Internal