Remove grpc dependency (#233)

Currently, the `grpc` dependency is causing the issue shown in issue
#231 due to an incompatibility with the most recent version of `grpc`
and any platform other than Linux based on our testing. We've also shown
reports that the prebuilt binaries downloaded by `gprc` are causing
massive bloat _**(nearly a 5x increase in size)**_ to our bundles that
are generated with the dependency included.

Upon investigation, we noticed that `grpc` isn't actually used by
anything in the library anymore, and was seemingly [added back by
mistake](#183) during the
most recent release, as `@grpc/grpc-js` is used in place of it.

Sources:
[Original PR](#125) to remove
`grpc`
[PR I made last year](#164),
where `grpc` was not in the list of dependencies at the time,
reinforcing the fact that it was added back by mistake
[The README of this very
repo](https://github.com/dgraph-io/dgraph-js?tab=readme-ov-file#install),
which has instructions to install `@grpc/grpc-js` and not `grpc`, and
[here is the PR](#182) where
that change was made

This PR is to remove the `grpc` dependency from the package to
accomplish the following:
- remedy the installation issue
- reduce install sizes
- get rid of an unused dependency