Unhide counter from mc_trks

In https://git.km3net.de/common/km3net-dataformat/-/issues/93 the counter field was added to Trk which is used in MC tracks. This needs to be unhidden from mc_tracks, which is done in this MR.

setup.cfg

@@ -54,7 +54,7 @@ where = src
 all =
 dev =
     black==21.6b0
-    km3net-testdata>=0.2.26
+    km3net-testdata>=0.3.2
     ipykernel
     matplotlib
     memory_profiler