[lldb] Nominate John Harrison and Ebuka Ezike as lldb-dap maintainers (#175031)

As the lead maintainer, I've been asked by the project council to
confirm that we have an up-to-date list of active maintainers for LLDB.

In light of that, I'd like to nominate Ebuka and John as lldb-dap
maintainer and replace Greg, who hasn't been active in this area
recently. I did not move Greg to "former maintainer" as he's still
listed for other components.

As a reminder, our community policies regarding the responsibilities of
maintainers can be found here:
https://llvm.org/docs/DeveloperPolicy.html#maintainers.

GitOrigin-RevId: 7e7d9dc0ee8209d8d1f0b254e2386ec70b4847e5