Update wildcard-query.asciidoc (#20057)

Update sentence grammar

docs/reference/query-dsl/wildcard-query.asciidoc

@@ -4,7 +4,7 @@
 Matches documents that have fields matching a wildcard expression (*not
 analyzed*). Supported wildcards are `*`, which matches any character
 sequence (including the empty one), and `?`, which matches any single
-character. Note this query can be slow, as it needs to iterate over many
+character. Note that this query can be slow, as it needs to iterate over many
 terms. In order to prevent extremely slow wildcard queries, a wildcard
 term should not start with one of the wildcards `*` or `?`. The wildcard
 query maps to Lucene `WildcardQuery`.