Update ProjectHistory.cpp (#687)

Fix typo - "Warning" instead of "Warining"

src/ProjectHistory.cpp

@@ -81,7 +81,7 @@ namespace {
       if ( !projectFileIO.AutoSave() )
          throw SimpleMessageBoxException{
             XO("Automatic database backup failed."),
-            XO("Warining"),
+            XO("Warning"),
             "Error:_Disk_full_or_not_writable"
          };
    }