Bug 23322: Correct case for boolean in ES search

Bug 23322: Correct case for boolean in ES search

I did not include tests only because this is a very small reasonable change and routine has no tests.
It does not affect behaviour, it only touches syntax lightly.

To test:
  0 - Set SearchEngine to ElasticSearch
  1 - Import the example record (a version is included in sample data in devbox/testing docker so you can skip)
  2 - Stage the attached example record
  3 - Match using 'ISBN' rule
  4 - No matches found
  5 - Apply patch
  6 - Restart all the things
  7 - Reapply matching with no rule
  8 - Reapply with ISBN matcing
  9 - It matches!
 10 - Set SearchEngine to Zebra
 11 - Reapply matching with no rule
 12 - Reapply with ISBN matching
 13 - Matching works as before in Zebra

Signed-off-by: Ron Houk <rhouk@ottumwapubliclibrary.org>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>