Change the environment variable placeholders to be consistent amongst…

[RossMacey]

… all example projects.

Short description of what this PR does:

This changes "SENDGRID_API" placeholder to the more widely used "NAME_OF_THE_ENVIRONMENT_VARIABLE_FOR_YOUR_SENDGRID_KEY" within the two example projects specified above. This keeps the environment variables consistent amongst all example projects as well as being completely unambiguous as to what should be placed here.

If you have questions, please send an email to Sendgrid, or file a Github Issue in this repository.

[SendGridDX]

All committers have signed the CLA.

[jonjenkins]

LGTM per https://sendgrid.com/blog/sendgrid-loves-developers/

[thinkingserious]

Hello @RossMacey,

Thanks again for the PR!

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Team SendGrid DX

[thinkingserious]

Hello @RossMacey,

Thanks again for the PR!

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Team SendGrid DX

[thinkingserious]

Hello @RossMacey,

Thanks again for the PR!

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

Please take a moment to checkout this link to find more issues to get you past the required threshold or to simply continue the celebration.

Also, please be sure you have officially registered with us here by November 1, 2018 to qualify.

If you have any questions you can email us at dx+hacktoberfest2018@sendgrid.com.

Thank you and Happy Hacktobering!

Team SendGrid