ARROW-5923: [C++][Parquet] Reword comment about UBSan and Int96 in writer.cc
ARROW-5923: [C++][Parquet] Reword comment about UBSan and Int96 in writer.cc

CC @fsaintjacques @pitrou

Author: Micah Kornfield <emkornfield@gmail.com>

Closes #4858 from emkornfield/fix_docs and squashes the following commits:

5294aa75b <Micah Kornfield> fix typo in comment

icexelloss/arrow,kou/arrow,laurentgo/arrow,icexelloss/arrow,renesugar/arrow,majetideepak/arrow,kou/arrow,laurentgo/arrow,xhochy/arrow,kou/arrow,apache/arrow,apache/arrow,xhochy/arrow,xhochy/arrow,renesugar/arrow,majetideepak/arrow,wesm/arrow,apache/arrow,xhochy/arrow,renesugar/arrow,icexelloss/arrow,apache/arrow,renesugar/arrow,renesugar/arrow,wesm/arrow,kou/arrow,wesm/arrow,majetideepak/arrow,wesm/arrow,xhochy/arrow,laurentgo/arrow,renesugar/arrow,majetideepak/arrow,cpcloud/arrow,kou/arrow,cpcloud/arrow,laurentgo/arrow,kou/arrow,cpcloud/arrow,cpcloud/arrow,laurentgo/arrow,xhochy/arrow,renesugar/arrow,cpcloud/arrow,majetideepak/arrow,wesm/arrow,laurentgo/arrow,wesm/arrow,kou/arrow,xhochy/arrow,renesugar/arrow,renesugar/arrow,icexelloss/arrow,icexelloss/arrow,wesm/arrow,majetideepak/arrow,cpcloud/arrow,icexelloss/arrow,apache/arrow,apache/arrow,laurentgo/arrow,majetideepak/arrow,kou/arrow,cpcloud/arrow,kou/arrow,laurentgo/arrow,laurentgo/arrow,majetideepak/arrow,wesm/arrow,xhochy/arrow,wesm/arrow,laurentgo/arrow,cpcloud/arrow,xhochy/arrow,kou/arrow,laurentgo/arrow,cpcloud/arrow,majetideepak/arrow,renesugar/arrow,cpcloud/arrow,cpcloud/arrow,apache/arrow,majetideepak/arrow,icexelloss/arrow,majetideepak/arrow,laurentgo/arrow,kou/arrow,majetideepak/arrow,icexelloss/arrow,icexelloss/arrow,laurentgo/arrow,majetideepak/arrow,apache/arrow,xhochy/arrow,apache/arrow,xhochy/arrow,xhochy/arrow,renesugar/arrow,laurentgo/arrow,icexelloss/arrow,xhochy/arrow,icexelloss/arrow,wesm/arrow,majetideepak/arrow,renesugar/arrow,icexelloss/arrow,icexelloss/arrow,renesugar/arrow,apache/arrow,kou/arrow,apache/arrow,renesugar/arrow,cpcloud/arrow,laurentgo/arrow,wesm/arrow,apache/arrow,wesm/arrow,cpcloud/arrow,apache/arrow,xhochy/arrow,renesugar/arrow,xhochy/arrow,wesm/arrow,kou/arrow,apache/arrow,majetideepak/arrow,kou/arrow,icexelloss/arrow,cpcloud/arrow,wesm/arrow