Update get-settings.asciidoc
Update get-settings.asciidoc

Fix syntax for filtering settings by name

Closes https://github.com/elastic/elasticsearch/issues/21713
strapdata/elassandra5-rc,strapdata/elassandra5-rc,strapdata/elassandra5-rc,strapdata/elassandra5-rc,strapdata/elassandra5-rc