Fix regression_test.sh deleterandom duration (#10437)

Summary:
deleterandom tests are too fast to get good signal, e.g.
--deletes=31250 in 0.170 seconds vs. --reads=1500000 in 288.491
seconds for readrandom. Removing the special handling (unknown
motivation in faa7eb3b) should suffice.

Pull Request resolved: https://github.com/facebook/rocksdb/pull/10437

Test Plan: watch continuous results

Reviewed By: ltamasi

Differential Revision: D38261185

Pulled By: pdillinger

fbshipit-source-id: 0f1b1b19efccda5689027d36cc2f01307f36031d

tools/regression_test.sh

@@ -139,10 +139,10 @@ function main {
       build_checkpoint
       run_db_bench "readrandom"
       run_db_bench "readwhilewriting"
-      run_db_bench "deleterandom" $((NUM_KEYS / 10 / $NUM_THREADS))
+      run_db_bench "deleterandom"
       run_db_bench "seekrandom"
       run_db_bench "seekrandomwhilewriting"
-      run_db_bench "multireadrandom" 
+      run_db_bench "multireadrandom"
   fi
 
   cleanup_test_directory $TEST_ROOT_DIR