Resolve "MR widget "copy branch name" button tooltip occasionally shows `undefined`"

What does this MR do?

Shortens the timeout period (from 300ms to 100ms) for setting the tooltip title for clipboard icon.

This fixes #268144 (closed) (initially reported in slack - https://gitlab.slack.com/archives/CETG54GQ0/p1602782877395400).

Also please see the reason behind the use of setTimeout !45035 (comment 429169526).

Conformity

• Changelog entry
• [-] Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• [-] Separation of EE specific content

Related to #268144 (closed)