Typo: Hearbeats in endpoint heartbeats warning dialog

TYPO in WARNING dialog box on Configuration > ENDPOINT HEARTBEATS tab:

>  Warning: The list of endpoints below only contains endpoints with the **hearbeats** plug-in installed...

Hearbeats should be heartbeats

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*Technical information if reporting a bug:*

- **ServicePulse version:** v1.14.4
- **ServiceControl version:** v3.1.1
- **Browser version:**  Edge
