build: remove inline-specifiers pnpm option

Remove the `use-inline-specifiers-lockfile-format=true` pnpm option
from our `.npmrc` file.

This was added in
[PNPM version v7.7.0](https://github.com/pnpm/pnpm/releases/tag/v7.7.0)
and should make our `pnpm-lock.yaml` file much nicer,
but unfortunately, renovate doesn't seem to support it (unsure why?).

This means that whenever we do a `pnpm install` locally, the lock-file
gets changed, and whenever renovate makes a PR, it changes the
lock-file back. This causes a lot of unnecassary merge conflicts.

.npmrc

@@ -1,3 +1,2 @@
 auto-install-peers=true
 strict-peer-dependencies=false
-use-inline-specifiers-lockfile-format=true