Fix miller indices display in pole figures

[psavery]

Overview

Recent changes to numpy would make the titles render like this:

np.int64(1), np.int64(1), np.int64(1)

Our conversion to an int before a string fixes them to be:

1, 1, 1

Affected Workflows

Powder, WPPF, for pole figures only

Documentation Changes

None

[codecov]

Codecov Report

❌ Patch coverage is 0% with 4 lines in your changes missing coverage. Please review.
✅ Project coverage is 70.90%. Comparing base (625a795) to head (aaa2ab8).
⚠️ Report is 6 commits behind head on master.

Files with missing lines	Patch %	Lines
hexrd/powder/wppf/texture.py	0.00%	4 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #906      +/-   ##
==========================================
- Coverage   70.90%   70.90%   -0.01%     
==========================================
  Files         143      143              
  Lines       22064    22076      +12     
==========================================
+ Hits        15645    15652       +7     
- Misses       6419     6424       +5     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.