Fix swapped tooltips for "Number of Samples" for "Transfer Rate" and "Access Time"

In the benchmark dialog, there are two values for the number of samples, one for the transfer rate, and the other for the access time measurements. The tooltips for the two are swapped. Attached patch corrects this error.

I do not know if the .po translation files would need to be fixed in addition to this, but just wanted to bring this minor bug to attention.