Fix various typos in the documentation

[spencerbyw]

Description of the change:
Fixes for a couple wording issues I found while reading through the docs.
Reason for the change:
Fix wording.
Link to original source:

N/A

[SendGridDX]

All committers have signed the CLA.

[thinkingserious]

Hello @spencerbyw,

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[thinkingserious]

Hello @spencerbyw,

Thanks again for the PR!

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[thinkingserious]

Hello @spencerbyw,

Thanks again for the PR!

You have earned 1 out of the 5 points needed to receive glorious SendGrid Hacktoberfest swag.

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