pgAdmin 4 commit: Proper error should be thrown when server group iscr

Proper error should be thrown when server group is created with existing name. Fixes #3693

Branch
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master

Details
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https://git.postgresql.org/gitweb?p=pgadmin4.git;a=commitdiff;h=2a359d9d774c8170d5e128fd05825e977409313f
Author: Aditya Toshniwal <aditya.toshniwal@enterprisedb.com>

Modified Files
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docs/en_US/release_notes.rst                  | 1 +
docs/en_US/release_notes_4_2.rst              | 1 +
web/pgadmin/browser/server_groups/__init__.py | 5 +++++
3 files changed, 7 insertions(+)