Remove @ni/beachball-lock-update and update version of beachball (#109)

# Justification

We were using the `@ni/beachball-lock-update` package to work around [a
bug](microsoft/beachball#525) with how
beachball modifies `package-lock.json` when publishing. That bug has
been addressed in more recent versions of beachball so we can stop using
the workaround.

This moves us towards fixing [this Nimble
issue](ni/nimble#601).

# Implementation

1. Remove `@ni/beachball-lock-update` from `package.json` and
`beachball.config.js`.
2. Install the latest version of `beachball`

# Testing

1. We've been running with this setup in Nimble for a few months and
it's worked well
2. I verified that basic beachball commands still work
3. I'll monitor the publishing pipeline as future changes go in. I
considered making a trivial edit to a pakckage to trigger a publish but
that seems pretty noisy now that our apps uptake new versions every
night.