fix issue #406 by going back to use areascale in applyGeometry

Release notes

use areascale again to set x axis label limits.

Details

Issue #406 (closed) is caused by the changes to TQPlotter::applyGeometry in e26aab3417f1d7a248129c25d2fbcd254368faaf by @cburgard. In particular, by not using the areascale variable anymore.

At least this is the case with ROOT 6.20/06 from AnalysisBase,21.2.204.

Requesting a check by @cburgard that this does not break plotting for other analyses.

Closes #406 (closed)