[DOCS] Update getting-started.asciidoc (#29518)
[DOCS] Update getting-started.asciidoc (#29518)

Highlighted that you can change shard counts using `_shrink` and `_split`.
gfyoung/elasticsearch,robin13/elasticsearch,uschindler/elasticsearch,gfyoung/elasticsearch,HonzaKral/elasticsearch,GlenRSmith/elasticsearch,gingerwizard/elasticsearch,nknize/elasticsearch,robin13/elasticsearch,robin13/elasticsearch,scorpionvicky/elasticsearch,coding0011/elasticsearch,gingerwizard/elasticsearch,coding0011/elasticsearch,uschindler/elasticsearch,GlenRSmith/elasticsearch,robin13/elasticsearch,GlenRSmith/elasticsearch,gingerwizard/elasticsearch,scorpionvicky/elasticsearch,gingerwizard/elasticsearch,gfyoung/elasticsearch,gfyoung/elasticsearch,nknize/elasticsearch,gingerwizard/elasticsearch,GlenRSmith/elasticsearch,coding0011/elasticsearch,HonzaKral/elasticsearch,coding0011/elasticsearch,uschindler/elasticsearch,scorpionvicky/elasticsearch,HonzaKral/elasticsearch,coding0011/elasticsearch,nknize/elasticsearch,GlenRSmith/elasticsearch,uschindler/elasticsearch,gingerwizard/elasticsearch,scorpionvicky/elasticsearch,robin13/elasticsearch,HonzaKral/elasticsearch,nknize/elasticsearch,gingerwizard/elasticsearch,scorpionvicky/elasticsearch,uschindler/elasticsearch,nknize/elasticsearch,gfyoung/elasticsearch