Fix reference to XContentBuilder.string() (#31337)
Fix reference to XContentBuilder.string() (#31337)

In 6.3 this was moved to `Strings.toString(XContentBuilder)` as part of the
XContent extraction. This commit fixes the docs to reference the new method.

Resolves #31326
uschindler/elasticsearch,robin13/elasticsearch,nknize/elasticsearch,coding0011/elasticsearch,nknize/elasticsearch,gfyoung/elasticsearch,robin13/elasticsearch,gingerwizard/elasticsearch,scorpionvicky/elasticsearch,coding0011/elasticsearch,gingerwizard/elasticsearch,uschindler/elasticsearch,GlenRSmith/elasticsearch,gfyoung/elasticsearch,scorpionvicky/elasticsearch,gfyoung/elasticsearch,HonzaKral/elasticsearch,robin13/elasticsearch,uschindler/elasticsearch,gfyoung/elasticsearch,scorpionvicky/elasticsearch,gingerwizard/elasticsearch,uschindler/elasticsearch,scorpionvicky/elasticsearch,gingerwizard/elasticsearch,gingerwizard/elasticsearch,GlenRSmith/elasticsearch,GlenRSmith/elasticsearch,GlenRSmith/elasticsearch,HonzaKral/elasticsearch,robin13/elasticsearch,uschindler/elasticsearch,nknize/elasticsearch,gingerwizard/elasticsearch,scorpionvicky/elasticsearch,robin13/elasticsearch,gingerwizard/elasticsearch,nknize/elasticsearch,HonzaKral/elasticsearch,coding0011/elasticsearch,coding0011/elasticsearch,gfyoung/elasticsearch,coding0011/elasticsearch,HonzaKral/elasticsearch,GlenRSmith/elasticsearch,nknize/elasticsearch