Docs - remove experimental marker from significant_text aggregation (#34598)

Author: markharwood

docs/reference/aggregations/bucket/significanttext-aggregation.asciidoc

@@ -1,8 +1,6 @@
 [[search-aggregations-bucket-significanttext-aggregation]]
 === Significant Text Aggregation
 
-experimental[]
-
 An aggregation that returns interesting or unusual occurrences of free-text terms in a set.
 It is like the <<search-aggregations-bucket-significantterms-aggregation,significant terms>> aggregation but differs in that:
 
@@ -27,8 +25,6 @@ The significant words are the ones that have undergone a significant change in p
 If the term "H5N1" only exists in 5 documents in a 10 million document index and yet is found in 4 of the 100 documents that make up a user's search results
 that is significant and probably very relevant to their search. 5/10,000,000 vs 4/100 is a big swing in frequency.
 
-experimental[The `significant_text` aggregation is new and may change in non-backwards compatible ways if we add further text-analysis features e.g. phrase detection]
-
 ==== Basic use
 
 In the typical use case, the _foreground_ set of interest is a selection of the top-matching search results for a query