`Data.IntMap.CharMap2` uses deprecated `Data.IntMap.showTree`

[andreasabel]

Compiler warning: Data.IntMap.CharMap2 uses deprecated Data.IntMap.showTree:

Building library for regex-tdfa-1.3.1.0..
[ 1 of 25] Compiling Data.IntMap.CharMap2 ( lib/Data/IntMap/CharMap2.hs, dist/build/Data/IntMap/CharMap2.o )

lib/Data/IntMap/CharMap2.hs:258:24: warning: [-Wdeprecations]
    In the use of ‘showTree’
    (imported from Data.IntMap, but defined in containers-0.5.11.0:Data.IntMap.Internal.DeprecatedDebug):
    Deprecated: "These debugging functions will be removed from this module. They are available from Data.IntMap.Internal.Debug."
    |
258 | showTree (CharMap m) = MD.showTree m
    |                        ^^^^^^^^^^^