Add missing cache=True to numba compilation

[maxnoe]

This shaved of a third of the import time (of course only of the second import) of ctapipe.io as reported by @GernotMaier here: #2476

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (b175f69) 92.46% compared to head (61f4062) 92.46%.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2477   +/-   ##
=======================================
  Coverage   92.46%   92.46%           
=======================================
  Files         234      234           
  Lines       19868    19868           
=======================================
  Hits        18370    18370           
  Misses       1498     1498           

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[maxnoe]

Unfortunately, most of the remaining time is spent on importing tables.leaf, about a second on my machine, so that's out of our direct control.