t1005: update test description

Problem: There is a test in t1005-max-jobs-limits.t that submits two
jobs to the priority plugin under the same bank using two different
methods: by default and by explicitly setting it with --setattr.
However, the test description is confusing and could be worded better.

Update the test description to more concisely describe what is
happening in the test.

t/t1005-max-jobs-limits.t

@@ -125,7 +125,7 @@ test_expect_success 'a submitted job while at max-running-jobs limit will have a
 	flux cancel ${jobid2}
 '
 
-test_expect_success 'submit max number of jobs with a mix of default bank and explicitly set bank' '
+test_expect_success 'submit max number of jobs to the same bank (explicitly and by default)' '
 	jobid1=$(flux python ${SUBMIT_AS} 5011 sleep 60) &&
 	jobid2=$(flux python ${SUBMIT_AS} 5011 --setattr=system.bank=account3 -n 1 sleep 60)
 '