reflect the wangle github branch rename from master to main
reflect the wangle github branch rename from master to main

Summary:
The primary branch in the GitHub wangle repository has been renamed from
`master` to `main`.  Update the getdeps manifest to reflect this, so that
getdeps builds correctly clone the repository.

Reviewed By: xavierd

Differential Revision: D30822418

fbshipit-source-id: 9670fff1e85e77adf84485ff8f2236f8826630ef

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