WL#7010: Remove unused --basedir and --datadir options from mysql_upgrade

Affects: Server-5.7   —   Status: Complete   —   Priority: Medium

% mysql_upgrade --help
...
  -b, --basedir=name  Not used by mysql_upgrade. Only for backward
                      compatibility.
...
  -d, --datadir=name  Not used by mysql_upgrade. Only for backward
                      compatibility.

These two options are unused. There is no reason to carry them forward.