Use constant instead of plain key name for device info connections in roborock and roomba

[jpbede]

Proposed change

Use the constant ATTR_CONNECTIONS instead of the plain key name for device info connections introduced with #103176 (roomba) and #103175 (roborock).

I didn't know that we have a constant for this.

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Hey there @humbertogontijo, @Lash-L, mind taking a look at this pull request as it has been labeled with an integration (roborock) you are listed as a code owner for? Thanks!

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Hey there @pschmitt, @cyr-ius, @shenxn, @Xitee1, mind taking a look at this pull request as it has been labeled with an integration (roomba) you are listed as a code owner for? Thanks!

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