docs: update DENO_DEPLOY_APPLICATION_SLUG to DENO_DEPLOY_APP_SLUG

[gentlementlegen]

The documentation states that the variable DENO_DEPLOY_APPLICATION_SLUG contains the human-readable slug for the app, whereas DENO_DEPLOY_APP_SLUG seems to be the variable that is actually populated.

This can be checked creating an App and adding a build step with:

echo "$DENO_DEPLOY_APP_SLUG"

which will yield the proper value, while

echo "$DENO_DEPLOY_APPLICATION_SLUG"

Will yield nothing.

[crowlKats]

@gentlementlegen thanks for this; would you be able to update the other env vars too?
they hsould be

DENO_DEPLOY_ORG_ID
DENO_DEPLOY_ORG_SLUG
DENO_DEPLOY_APP_ID

[gentlementlegen]

@crowlKats Updated in b9d3046

[crowlKats]

@gentlementlegen thanks! could you run the formatter, and then we can land this

[gentlementlegen]

@crowlKats CI is green now!

[crowlKats]

LGTM, thanks!