Fix duplicate note x-refs in mapping.asciidoc (#37904)
Fix duplicate note x-refs in mapping.asciidoc (#37904)

The docs silently accept duplicate note markers (such as `<3>` here) but
formats them in an unexpected way. This change removes this duplication so that
the rendered documentation looks as intended.
uschindler/elasticsearch,robin13/elasticsearch,gingerwizard/elasticsearch,HonzaKral/elasticsearch,nknize/elasticsearch,uschindler/elasticsearch,GlenRSmith/elasticsearch,gingerwizard/elasticsearch,gingerwizard/elasticsearch,robin13/elasticsearch,scorpionvicky/elasticsearch,HonzaKral/elasticsearch,GlenRSmith/elasticsearch,uschindler/elasticsearch,nknize/elasticsearch,scorpionvicky/elasticsearch,coding0011/elasticsearch,scorpionvicky/elasticsearch,scorpionvicky/elasticsearch,uschindler/elasticsearch,uschindler/elasticsearch,GlenRSmith/elasticsearch,nknize/elasticsearch,nknize/elasticsearch,gingerwizard/elasticsearch,gingerwizard/elasticsearch,gingerwizard/elasticsearch,coding0011/elasticsearch,HonzaKral/elasticsearch,robin13/elasticsearch,robin13/elasticsearch,coding0011/elasticsearch,coding0011/elasticsearch,nknize/elasticsearch,HonzaKral/elasticsearch,robin13/elasticsearch,GlenRSmith/elasticsearch,scorpionvicky/elasticsearch,coding0011/elasticsearch,GlenRSmith/elasticsearch,gingerwizard/elasticsearch