Update deprecation-of-splunk-on-call-phone-notifications-to-china.rst

[cmillane-splunk]

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Describe the change

Corrected a typo on the word Phone in the title of the article

[cmillane-splunk]

Hey @pauljwil , thanks for merging this! I was wondering if there may be some kind of propagation time for the change to be reflected on the site or some other action I should take? Noticing that when I open https://docs.splunk.com/observability/en/sp-oncall/admin/get-started/deprecation-of-splunk-on-call-phone-notifications-to-china.html, I still see the typo listed