Updated api.specification.md to adhere to gatsby style guide

[adibfirman]

Description

Avoid pronoun "we" and replace those with "you"

Related issues

in here #18284

[adibfirman]

@marcysutton Hey there , so this is my very first pull request . So i would like to know if this is fine or let me know if any changes are required. Hope that's fine.

[gatsbot]

Holy buckets, @adibfirman — we just merged your PR to Gatsby! 💪💜

Gatsby is built by awesome people like you. Let us say “thanks” in two ways:

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Thanks again!

[marcysutton]

Super cool, thanks for the PR!