fix: fix iris example to use reported metric name

[azhou-determined]

Ticket

Description

keras's metrics.categorical_accuracy is categorical_accuracy, not val_categorical_accuracy

Test Plan

Checklist

• Changes have been manually QA'd
• New features have been approved by the corresponding PM
• User-facing API changes have the "User-facing API Change" label
• Release notes have been added as a separate file under docs/release-notes/
  See Release Note for details.
• Licenses have been included for new code which was copied and/or modified from any external code

[netlify]

✅ Deploy Preview for determined-ui canceled.

Name	Link
🔨 Latest commit	f38e8f9
🔍 Latest deploy log	https://app.netlify.com/sites/determined-ui/deploys/67225d43c1607700083f2d77

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 58.47%. Comparing base (4d75d94) to head (f38e8f9).

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #10155      +/-   ##
==========================================
+ Coverage   54.26%   58.47%   +4.20%     
==========================================
  Files        1259      754     -505     
  Lines      157285   104301   -52984     
  Branches     3643     3642       -1     
==========================================
- Hits        85354    60987   -24367     
+ Misses      71798    43181   -28617     
  Partials      133      133              

Flag	Coverage Δ
backend	43.80% <ø> (-2.12%)	⬇️
harness	71.15% <ø> (ø)
web	54.30% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

see 505 files with indirect coverage changes