Restore default port for `adb connect`.

The default port of 5555 was removed a while back, but the help text was
never updated, and other contexts still allow a default port.

Bug: https://issuetracker.google.com/128561172
Test: manual
Change-Id: I6e5e6edeb2243386a0301c0a6cad569189f9910e
3 files changed