Remove os_must_gather timeout on wntp jobs

Currently this value is using an int value, but it should be a
string value. This causes that on those jobs the must_gather
is not collected.

Dropping the value as relying on the default 30m should be
enough.

Signed-off-by: Arnau Verdaguer <averdagu@redhat.com>

Author: averdagu

zuul.d/whitebox_neutron_tempest_jobs.yaml

@@ -15,7 +15,6 @@
       deployment by running whitebox-neutron-tempest-plugin tests.
     vars:
       cifmw_run_test_role: test_operator
-      cifmw_os_must_gather_timeout: 28800
       cifmw_test_operator_timeout: 14400
       cifmw_block_device_size: 40G
       cifmw_test_operator_tempest_concurrency: 6