Revert "Set volume_step in monoprice media_player"

[emontnemery]

Reverts #105670

There was some additional issues brought up in home-assistant/architecture#1012 after this PR was merged. This functionality needs to be reverted until they way forward is clear.

[home-assistant]

Hey there @etsinko, @OnFreund, mind taking a look at this pull request as it has been labeled with an integration (monoprice) you are listed as a code owner for? Thanks!

Code owner commands

Code owners of monoprice can trigger bot actions by commenting:

• @home-assistant close Closes the pull request.
• @home-assistant rename Awesome new title Renames the pull request.
• @home-assistant reopen Reopen the pull request.
• @home-assistant unassign monoprice Removes the current integration label and assignees on the pull request, add the integration domain after the command.
• @home-assistant add-label needs-more-information Add a label (needs-more-information, problem in dependency, problem in custom component) to the pull request.
• @home-assistant remove-label needs-more-information Remove a label (needs-more-information, problem in dependency, problem in custom component) on the pull request.