Update csh-ldap requirement from ~=2.1.0 to ~=2.3.1 (#229)

Updates the requirements on [csh-ldap](https://github.com/liam-middlebrook/csh_ldap) to permit the latest version.
- [Release notes](https://github.com/liam-middlebrook/csh_ldap/releases)
- [Changelog](https://github.com/liam-middlebrook/csh_ldap/blob/master/ChangeLog)
- [Commits](liam-middlebrook/csh_ldap@2.1.0...2.3.1)

Signed-off-by: dependabot[bot] <[email protected]>

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

requirements.txt

@@ -7,7 +7,7 @@ psycopg2-binary~=2.8.6
 Flask-Migrate~=2.2.1
 pylint~=2.6.0
 gunicorn~=20.0.4
-csh_ldap~=2.1.0
+csh_ldap~=2.3.1
 onesignal-sdk~=1.0.0
 pylint-quotes~=0.2.1
 sentry-sdk~=0.19.5