Tweaking classifying algorithm constants to reduce false positives.

scripts/slave/recipe_modules/auto_bisect/example.expected/android_bisector.json

 [
   {
     "cmd": [
       "git",
       "update-ref",
       "refs/heads/master",
       "refs/remotes/origin/master"
     ],
     "cwd": "[TMP_BASE]/fake_checkout_tmp_1",
     "name": "git update-ref"
@@ skipping 575 matching lines @@
       "@@@STEP_NEST_LEVEL@1@@@"
     ]
   },
   {
     "cmd": [
       "python",
       "-u",
       "RECIPE_MODULE[build::auto_bisect]/resources/significantly_different.py",
       "[19, 20, 21, 22, 23]",
       "[12, 13, 14, 15, 16]",
-      "0.01"
+      "0.005"
     ],
     "cwd": "[SLAVE_BUILD]",
     "name": "Waiting for chromium@dcdcdc0ff1.Checking sample difference",
     "stdout": "/path/to/tmp/json",
     "~followup_annotations": [
       "@@@STEP_NEST_LEVEL@1@@@",
       "@@@STEP_LOG_LINE@json.output (invalid)@null@@@",
       "@@@STEP_LOG_END@json.output (invalid)@@@"
     ]
   },
   {
     "cmd": [
       "python",
       "-u",
       "RECIPE_MODULE[build::auto_bisect]/resources/significantly_different.py",
       "[12, 13, 14, 15, 16]",
       "[12, 13, 14, 15, 16]",
-      "0.01"
+      "0.005"
     ],
     "cwd": "[SLAVE_BUILD]",
     "name": "Waiting for chromium@dcdcdc0ff1.Checking sample difference (2)",
     "stdout": "/path/to/tmp/json",
     "~followup_annotations": [
       "@@@STEP_NEST_LEVEL@1@@@",
       "@@@STEP_LOG_LINE@json.output (invalid)@null@@@",
       "@@@STEP_LOG_END@json.output (invalid)@@@"
     ]
   },
@@ skipping 204 matching lines @@
       "@@@STEP_LOG_LINE@json.output@}@@@",
       "@@@STEP_LOG_END@json.output@@@"
     ]
   },
   {
     "name": "$result",
     "recipe_result": null,
     "status_code": 0
   }
 ]