Switch from abandoned dgrijalva/jwt-go to golang-jwt/jwt

[rowanseymour]

See https://github.com/nyaruka/mailroom/security/dependabot/go.mod/github.com%2Fdgrijalva%2Fjwt-go/open

[codecov]

Codecov Report

Merging #469 (f9d59a3) into main (88c97aa) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main     #469   +/-   ##
=======================================
  Coverage   56.97%   56.97%           
=======================================
  Files         123      123           
  Lines        8591     8591           
=======================================
  Hits         4895     4895           
  Misses       2920     2920           
  Partials      776      776           

Impacted Files	Coverage Δ
core/ivr/vonage/vonage.go	20.63% <ø> (ø)

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