pgAdmin 4 commit: Fix accessibility issues:

Fix accessibility issues:
1) Suppress ESC key presses in Alertify dialogues when the come from Select2 controls (It also closes the alertify
dialogwhen user try to close Select2 using ESC key) 
2) Do not allow Tabindex focus on Switch control when it is disbaled
3) Tab keyboard shortcut navigation does not work in wcDocker iframe.

Fixes #4935

Branch
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master

Details
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https://git.postgresql.org/gitweb?p=pgadmin4.git;a=commitdiff;h=6a5d98cf19a02fc83b3000292c9dcaf7d6dadee0
Author: Murtuza Zabuawala <murtuza.zabuawala@enterprisedb.com>

Modified Files
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docs/en_US/release_notes_4_16.rst                  | 1 +
web/pgadmin/browser/static/js/keyboard.js          | 5 +++--
web/pgadmin/static/js/alertify.pgadmin.defaults.js | 2 +-
web/pgadmin/static/js/backform.pgadmin.js          | 3 ++-
4 files changed, 7 insertions(+), 4 deletions(-)