Remove deprecated timeMode parameter for CBC compatibility

MIPster/CBC no longer supports the 'timeMode' parameter. Removed the
cbc_set_parameter(self, "timeMode", "elapsed") call which caused
immediate exit with 'Unrecognized parameter' error.

Time limits are still set correctly via set_max_seconds().

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: h-g-s

mip/cbc.py

@@ -1630,7 +1630,6 @@ def set_processing_limits(
         smaller limits could have been set in a previous iteration"""
 
         if max_time != mip.INF:
-            cbc_set_parameter(self, "timeMode", "elapsed")
             self.set_max_seconds(max_time)
         if max_nodes != mip.INT_MAX:
             self.set_max_nodes(max_nodes)