Allow community managers to be a trio
Allow community managers to be a trio

For the 2019 setup we decided to have a trio of community managers.
Adapt the documentation to cover this setup.

Signed-off-by: Edwin Kempin <d43fb6c98c97e553b671ed9a9318100f1de386e7@google.com>
Change-Id: I95127ba6bf8e57f43aef8f157fdbe2c21abe9be3

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