Remove obsolete and misleading comment

The tenant ID was not actually generated here but in NeonEnvBuilder.
And the "neon_local init" command hasn't been able to generate the
initial tenant since 8712e1899e anyway.

test_runner/fixtures/neon_fixtures.py

@@ -1073,9 +1073,6 @@ class NeonEnv:
         self.pg_distrib_dir = config.pg_distrib_dir
         self.endpoint_counter = 0
         self.storage_controller_config = config.storage_controller_config
-
-        # generate initial tenant ID here instead of letting 'neon init' generate it,
-        # so that we don't need to dig it out of the config file afterwards.
         self.initial_tenant = config.initial_tenant
         self.initial_timeline = config.initial_timeline