added warning in the example code refresh token

[lucascdsilva]

added warning: in the example code of automatic update of the
token access.

Fixes #<issue_number_goes_here> (it's a good idea to open an issue first for discussion)

• npm test succeeds
• Pull request has been squashed into 1 commit
• I did NOT manually make changes to anything in apis/
• Code coverage does not decrease (if any source code was changed)
• Appropriate JSDoc comments were updated in source code (if applicable)
• Approprate changes to readme/docs are included in PR

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[codecov-io]

Codecov Report

Merging #827 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #827   +/-   ##
=======================================
  Coverage   79.23%   79.23%           
=======================================
  Files           4        4           
  Lines         236      236           
  Branches       53       53           
=======================================
  Hits          187      187           
  Misses         30       30           
  Partials       19       19

Impacted Files	Coverage Δ
lib/apirequest.ts	97.26% <0%> (ø)	⬆️

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[lucascdsilva]

i signed (CLA)

[googlebot]

CLAs look good, thanks!