chore: Bump Axios to 0.21.4 to fix ReDoS

[LuisOsta]

Fixes issue #1294 . Based on the discussion here. It actually seems that 0.21.4 is what's necessary to address the fix.

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Fixes

I changed the version of axios that sendgrid client uses from 0.21.1 to 0.21.4.

Checklist

• I acknowledge that all my contributions will be made under the project's license
• I have made a material change to the repo (functionality, testing, spelling, grammar)
• I have read the Contribution Guidelines and my PR follows them
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• I have added tests that prove my fix is effective or that my feature works
• I have added the necessary documentation about the functionality in the appropriate .md file
• I have added inline documentation to the code I modified

[LuisOsta]

Thanks for the quick review! @bgdman

[LuisOsta]

@bgdman Do you have a sense about when this fix will be merged in?

[childish-sambino]

Unmarking this as breaking.