Remove unneeded JMapPane cast

Description

Without this change one has to create their own implementation of the `PanTool` class in order to extend `AbstractMapPane` class.

A pull request for this was submitted here: https://github.com/geotools/geotools/pull/2223

Environment

None

Status

Assignee

Unassigned

Reporter

Leif Gruenwoldt

Triage

None

Components

Fix versions

Affects versions

21-RC

Priority

Medium
Configure