PriceSetTest - Fix test-run on case-insensitive filesystem

[totten]

Before

The test internally+arbitrarily inconsistent about PriceFieldValue vs pricefieldvalue.

On case-insensitive filesystem, this leads to a test failure:

$ CIVICRM_UF=UnitTests phpunit8 tests/phpunit/CRM/Price/BAO/
PHPUnit 8.5.27 #StandWithUkraine

.
Installing dmastertest_qmzfj database
...
Fatal error: Cannot redeclare civicrm_api3_price_field_value_create() (previously declared in /Users/totten/bknix/build/dmaster/web/sites/all/modules/civicrm/api/v3/PriceFieldValue.php:31) in /Users/totten/bknix/build/dmaster/web/sites/all/modules/civicrm/api/v3/Pricefieldvalue.php on line 31

After

The test internally consistent. Test passes.

[yashodha]

test this please

[demeritcowboy]

The test passed before on windows for me but the patch is obviously correct so 🤷