ARROW-6419: [Website] Update Parquet perf results after reverting to jemalloc stable-4

diff --git a/_posts/2019-09-03-faster-strings-cpp-parquet.md b/_posts/2019-09-03-faster-strings-cpp-parquet.md
index e0d0b5d..23293f5 100644
--- a/_posts/2019-09-03-faster-strings-cpp-parquet.md
+++ b/_posts/2019-09-03-faster-strings-cpp-parquet.md
@@ -196,11 +196,11 @@
 
 Here, similarly reading `DictionaryArray` directly is many times faster.
 
-These benchmarks show that reading the dense binary data is slower in the
-master branch than in version 0.12.1, so we will need to do some profiling and
-see what we can do to bring read performance back in line. Optimizing the dense
-read path has not been too much of a priority relative to the dictionary read
-path in this work. See [ARROW-6417][12] for some investigation and discussion.
+These benchmarks show that parallel reads of dense binary data may be slightly
+slower though single-threaded reads are now faster. We may want to do some
+profiling and see what we can do to bring read performance back in
+line. Optimizing the dense read path has not been too much of a priority
+relative to the dictionary read path in this work.
 
 # Memory Use Improvements
 
diff --git a/img/20190903_parquet_read_perf.png b/img/20190903_parquet_read_perf.png
index d1b1fe8..fa4e4f5 100644
--- a/img/20190903_parquet_read_perf.png
+++ b/img/20190903_parquet_read_perf.png
Binary files differ
diff --git a/img/20190903_parquet_write_perf.png b/img/20190903_parquet_write_perf.png
index 4560607..2c91baf 100644
--- a/img/20190903_parquet_write_perf.png
+++ b/img/20190903_parquet_write_perf.png
Binary files differ