Remove code for internet explorer

[eliasecasta]

What does this PR do?

Removes no longer needed code to support internet explorer browser for the dropdown menus.

This PR potentially fixes Issue #6879

Where should the reviewer start?

src\js\components\Drop\StyledDrop.js

What testing has been done on this PR?

I was able to test the impact in chrome and firefox, I dont have a mac so I was unable to test it on Safari.

How should this be manually tested?

Adding extra text to the dropdown elements to check for text overflow.

Do Jest tests follow these best practices?

• screen is used for querying.
• The correct query is used. (Refer to this list of queries)
• userEvent is used in place of fireEvent.
• asFragment() is used for snapshot testing.

Any background context you want to provide?

What are the relevant issues?

Screenshots (if appropriate)

Chrome code disabled:

Edge code disabled:

Edge code enabled:

Firefox code disabled:

Do the grommet docs need to be updated?

No.

Should this PR be mentioned in the release notes?

No.

Is this change backwards compatible or is it a breaking change?

Backwards compatible.

[jcfilben]

Some of the jest snapshots need updated to reflect this change. You can update the snapshots by running yarn jest -u