Resolve name collision between S3 and Lightsail in quickstart

[mergenci]

Description of your changes

Fix #590: S3 and Lightsail APIs have their own “buckets” resources. Quickstart document creates an S3 bucket. When kubectl get buckets command is run, though, Lightsail resources are listed. Such behavior confuses users, especially newcomers to crossplane, who expect to see their S3 buckets instead.

I have:

• Run make reviewable test to ensure this PR is ready for review.

I couldn't run make reviewable test, because of IS#737. I hope that updating only documentation won't cause any problems.

How has this code been tested

I've followed quickstart document and manually run shell commands. I've used a local kind cluster.

[Upbound-CLA]

All committers have signed the CLA.

[turkenf]

Thank you @mergenci, LGTM.

[mergenci]

I wanted to run make reviewable test before merging, but it failed again 🤦‍♂️— this time for a different reason than above:

17:46:34 [ .. ] golangci-lint
WARN [runner] The linter 'interfacer' is deprecated (since v1.38.0) due to: The repository of the linter has been archived by the owner.  
ERRO Timeout exceeded: try increasing it by passing --timeout option 
17:57:14 [FAIL]
make[2]: *** [go.lint] Error 1
make[1]: *** [lint] Error 2
make: *** [reviewable] Error 2

I'll merge without running it. Everything should be fine.