MAINT: Removes unnecessary capital_base arg to TradingAlgorithm (#1677)

Capital base is included in the sim params, so we should define the
value there, or use the default.

This change also unifies the default capital base as 1e5, as was
previously defined in algorithm.py.

tests/test_algorithm.py

@@ -4278,7 +4278,6 @@ class TestEquityAutoClose(WithTmpDir, WithTradingCalendars, ZiplineTestCase):
             env=env,
             sim_params=resources.sim_params,
             data_frequency='minute',
-            capital_base=capital_base,
         )
 
         output = algo.run(resources.data_portal)