fix: correct id token type in token exchange response

[aeneasr]

Closes ory/client-go#2

Related issue(s)

Checklist

• I have read the contributing guidelines.
• I have referenced an issue containing the design document if my change
  introduces a new feature.
• I am following the
  contributing code guidelines.
• I have read the security policy.
• I confirm that this pull request does not address a security
  vulnerability. If this pull request addresses a security vulnerability, I
  confirm that I got the approval (please contact
  security@ory.sh) from the maintainers to push
  the changes.
• I have added tests that prove my fix is effective or that my feature
  works.
• I have added or changed the documentation.

Further Comments

[codecov]

Codecov Report

Merging #3625 (6975e8a) into master (af0d477) will increase coverage by 0.01%.
Report is 2 commits behind head on master.
The diff coverage is n/a.

❗ Current head 6975e8a differs from pull request most recent head 615725a. Consider uploading reports for the commit 615725a to get more accurate results

@@            Coverage Diff             @@
##           master    #3625      +/-   ##
==========================================
+ Coverage   76.16%   76.18%   +0.01%     
==========================================
  Files         133      133              
  Lines       10043    10043              
==========================================
+ Hits         7649     7651       +2     
+ Misses       1870     1868       -2     
  Partials      524      524              

Files Changed	Coverage Δ
oauth2/handler.go	67.94% <ø> (ø)

... and 1 file with indirect coverage changes