Fix quickstart link

[jdetter]

Description of Changes

Our current CLI outputs this when installing or upgrading:

The install process is complete; check out our quickstart guide to get started!
        <https://spacetimedb.com/docs/quick-start>

This link 404s, it should be:

The install process is complete; check out our quickstart guide to get started!
        <https://spacetimedb.com/docs/getting-started>

API and ABI breaking changes

If this is an API or ABI breaking change, please apply the
corresponding GitHub label.

Not breaking

Expected complexity level and risk

How complicated do you think these changes are? Grade on a scale from 1 to 5,
where 1 is a trivial change, and 5 is a deep-reaching and complex change.

This complexity rating applies not only to the complexity apparent in the diff,
but also to its interactions with existing and future code.

If you answered more than a 2, explain what is complex about the PR,
and what other components it interacts with in potentially concerning ways.

0

Testing

Describe any testing you've done, and any testing you'd like your reviewers to do,
so that you're confident that all the changes work as expected!

I downgraded the version of SpacetimeDB on this branch via:

Boppy@JASKIER MINGW64 ~/clockwork/SpacetimeDB/tools/upgrade-version (jdetter/fix-quickstart-link)
$ cargo run 1.0.0-rc7

Then I built the new update binary:

Boppy@JASKIER MINGW64 ~/clockwork/SpacetimeDB (jdetter/fix-quickstart-link)
$ cargo build --release -p spacetimedb-update
   Compiling smallvec v1.13.2
   Compiling scopeguard v1.2.0
   Compiling serde v1.0.215
...

Then I manually ran the update process:

Boppy@JASKIER MINGW64 ~/clockwork/SpacetimeDB/target/release (jdetter/fix-quickstart-link)
$ ./spacetimedb-update.exe self-install
The SpacetimeDB command line tool will now be installed into C:\Users\Boppy\AppData\Local\SpacetimeDB
Would you like to continue? yes
Downloading latest version...
  Installing v1.0.0: done!
  Self-updating `spacetime version`: done!
The `spacetime` command has been installed as C:\Users\Boppy\AppData\Local\SpacetimeDB\spacetime.exe

The install process is complete; check out our quickstart guide to get started!
        <https://spacetimedb.com/docs/getting-started>

(see the updated URL)

[bfops]

Seems right to me