Docs: Wrong class name

Was QFilterBuilders, should be FilterBuilders.

Closes #7611
Docs: Added explanation of how to do multi-field terms agg

Closes #5100
Docs: Update span-not-query.asciidoc

The example given does not clearly explain what the query does.

Closes #7049
Docs: Adds missing explanation to multi-match

Closes #7281
Docs: Update prefix-query.asciidoc

Typo (missing word)

Closes #7283
Docs: Clarify that refresh on get/update/delete just refreshes the relevant shards

Closes #7359
Docs: Update scripting.asciidoc

Clarify that doc[...] does not return objects

Closes #7384
Docs: Clarify that refresh on update just refreshes the relevant shards
Docs: Update regexp-syntax.asciidoc

Closes #7419