Rename amazon EMR hook name

[vinitpayal]

Renamed emr hook from Elastic MapReduce to Amazon Elastic MapReduce

Fixes for request at #20746 to make the hook naming consistent with other AWS hooks

^ Add meaningful description above

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[boring-cyborg]

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[github-actions]

The PR is likely OK to be merged with just subset of tests for default Python and Database versions without running the full matrix of tests, because it does not modify the core of Airflow. If the committers decide that the full tests matrix is needed, they will add the label 'full tests needed'. Then you should rebase to the latest main or amend the last commit of the PR, and push it with --force-with-lease.

[boring-cyborg]

Awesome work, congrats on your first merged pull request!