Update REXML version (#940)
Update REXML version (#940)

Updating REXML version to resolved a security vulnerability found by
dependabot which it could not resolve on its own. The message from
dependabot indicated:

The REXML gem before 3.2.5 in Ruby before 2.6.7, 2.7.x before 2.7.3,
and 3.x before 3.0.1 does not properly address XML round-trip issues.
An incorrect document can be produced after parsing and serializing.
thoughtbot/clearance,thoughtbot/clearance,thoughtbot/clearance