Fix custom options selection event

[cheenamalhotra]

Addresses #25378

Use Widget's value instead of value provided by selection event, which is diaplay value by design.

[coveralls]

Pull Request Test Coverage Report for Build 8009143295

Warning: This coverage report may be inaccurate.

This pull request's base commit is no longer the HEAD commit of its target branch. This means it includes changes from outside the original pull request, including, potentially, unrelated coverage changes.

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• For a quick fix, rebase this PR at GitHub. Your next report should be accurate.

Details

• -2 of 2 (0.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.002%) to 41.759%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
src/sql/workbench/services/connection/browser/connectionWidget.ts	0	2	0.0%

Totals
Change from base Build 8008775528:	0.002%
Covered Lines:	30828
Relevant Lines:	69082

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💛 - Coveralls