chore: fix typos

[leahecole]

Description

Fixes #

Note: It's a good idea to open an issue first for discussion.

Checklist

• I have followed Sample Guidelines from AUTHORING_GUIDE.MD
• README is updated to include all relevant information
• Tests pass: nox -s py-3.6 (see Test Environment Setup)
• Lint pass: nox -s lint (see Test Environment Setup)
• These samples need a new API enabled in testing projects to pass (let us know which ones)
• These samples need a new/updated env vars in testing projects set to pass (let us know which ones)
• Please merge this PR for me once it is approved.
• This sample adds a new sample directory, and I updated the CODEOWNERS file with the codeowners for this sample

[dandhlee]

same typo is found in other files: could you also update these?

./composer/rest/get_dag_prefix.py:        'location', help='Region of the Cloud Composer environent.')
./composer/rest/get_dag_prefix.py:        'composer_environment', help='Name of the Cloud Composer environent.')
./composer/rest/get_client_id.py:        'location', help='Region of the Cloud Composer environent.')
./composer/rest/get_client_id.py:        'composer_environment', help='Name of the Cloud Composer environent.')
./composer/rest/README.rst:      location              Region of the Cloud Composer environent.
./composer/rest/README.rst:      composer_environment  Name of the Cloud Composer environent.

[leahecole]

Oh dang @dandhlee good eyes! The README.rst is autogenned but I'll do a find and replace for environent :)

[leahecole]

I fixed the typos in the other file and as an added bonus added two usage comments as a first step for improvement (#5546 )

[dandhlee]

lint is slightly unhappy but otherwise LGTM!

[leahecole]

🙈 fixing now