Fix csuite compare command

csuite.py compare command currently throws exception

"_csv.Error: iterator should return strings, not bytes
(did you open the file in text mode?)"

This should fix it.

Change-Id: I69c0ec43575a8c3627dac81dc99e47ba6adf6f61
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2316833Reviewed-by: Michael Stanton <mvstanton@chromium.org>
Commit-Queue: Z Nguyen-Huu <duongn@microsoft.com>
Cr-Commit-Position: refs/heads/master@{#69050}

test/benchmarks/csuite/compare-baseline.py

@@ -189,7 +189,7 @@ def ProcessResults(opts, results, baselines):
       PrintSeparator(opts, baselines, False)
 
 def ProcessFile(file_path):
-  file_reader = csv.reader(open(file_path, 'rb'), delimiter=',')
+  file_reader = csv.reader(open(file_path, 'r'), delimiter=',')
   benchmark_results = {}
   current_rows = []
   for row in file_reader: