Update config to point to main branch

[nickzhums]

[nickzhums]

the current edit button points to master branch, not main branch example:

https://docs.microsoft.com/en-us/java/api/overview/azure/resourcemanager-appservice-readme?view=azure-java-stable

this causes problems when we are trying edit the docs, so creating this PR to make this change

[opbld34]

Docs Build status updates of commit 8cb940c:

:white_check_mark: Validation status: passed

File	Status	Preview URL	Details
.openpublishing.publish.config.json	:white_check_mark:Succeeded

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