Update subjects to include reference to UAT when inserted from UAT

[jordanpadams]

💡 Description

For all subject that are UAT subjects, include reference:

<subjects>
  <subject subjectScheme="UAT" schemeURI="http://astrothesaurus.org" valueURI="http://astrothesaurus.org/uat/890">Kreutz Sungrazers</subject>
  <subject subjectScheme="UAT" schemeURI="http://astrothesaurus.org" valueURI="http://astrothesaurus.org/uat/280">Comets</subject>
  <subject subjectScheme="UAT" schemeURI="http://astrothesaurus.org" valueURI="http://astrothesaurus.org/uat/313">Coronagraphic imaging</subject>
  <subject subjectScheme="UAT" schemeURI="http://astrothesaurus.org" valueURI="http://astrothesaurus.org/uat/1234">Photometry</subject>
</subjects>