Fixes

Fixes a typo "Subjuct" -> "Subject"

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[x] I have made a material change to the repo (functionality, testing, spelling, grammar)
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[ ] I have added tests that prove my fix is effective or that my feature works
[ ] I have added necessary documentation about the functionality in the appropriate .md file
[ ] I have added inline documentation to the code I modified

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sendgrid / sendgrid-python