pgAdmin 4 commit: 1) Source/Target database and schema should be select

1) Source/Target database and schema should be selected by default when the user selects any server in the schema diff
tool.
2) Added line break for the generated script if select multiple objects.
3) Remove reactivated RM from the release notes.

Branch
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master

Details
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https://git.postgresql.org/gitweb?p=pgadmin4.git;a=commitdiff;h=26cdda090ef501c5f56095073cb55ec028086cb8

Modified Files
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docs/en_US/release_notes_4_18.rst                  |  1 -
web/pgadmin/tools/schema_diff/__init__.py          |  6 +--
.../tools/schema_diff/static/js/schema_diff_ui.js  | 56 ++++++++++++++++++++--
3 files changed, 53 insertions(+), 10 deletions(-)