[Docs] Use capital letters in section headings (#31678)
[Docs] Use capital letters in section headings (#31678)

Section headings should start with capital letters.
robin13/elasticsearch,uschindler/elasticsearch,nknize/elasticsearch,scorpionvicky/elasticsearch,uschindler/elasticsearch,scorpionvicky/elasticsearch,GlenRSmith/elasticsearch,uschindler/elasticsearch,robin13/elasticsearch,coding0011/elasticsearch,uschindler/elasticsearch,nknize/elasticsearch,gfyoung/elasticsearch,robin13/elasticsearch,gingerwizard/elasticsearch,gingerwizard/elasticsearch,robin13/elasticsearch,gfyoung/elasticsearch,gingerwizard/elasticsearch,gingerwizard/elasticsearch,HonzaKral/elasticsearch,HonzaKral/elasticsearch,GlenRSmith/elasticsearch,coding0011/elasticsearch,gfyoung/elasticsearch,coding0011/elasticsearch,HonzaKral/elasticsearch,GlenRSmith/elasticsearch,gingerwizard/elasticsearch,scorpionvicky/elasticsearch,HonzaKral/elasticsearch,scorpionvicky/elasticsearch,uschindler/elasticsearch,coding0011/elasticsearch,GlenRSmith/elasticsearch,nknize/elasticsearch,GlenRSmith/elasticsearch,coding0011/elasticsearch,gingerwizard/elasticsearch,gingerwizard/elasticsearch,gfyoung/elasticsearch,nknize/elasticsearch,nknize/elasticsearch,scorpionvicky/elasticsearch,gfyoung/elasticsearch,robin13/elasticsearch