[DOCS] Remove unneeded ifdef::asciidoctor[] conditionals (#42758)

    Several `ifdef::asciidoctor` conditionals were added so that AsciiDoc
    and Asciidoctor doc builds rendered consistently.

    With elastic/docs#827, Elasticsearch Reference
    documentation migrated completely to Asciidoctor. We no longer need to
    support AsciiDoc so we can remove these conditionals.

    Resolves #41722

docs/reference/aggregations/pipeline/movavg-aggregation.asciidoc

@@ -1,14 +1,7 @@
 [[search-aggregations-pipeline-movavg-aggregation]]
 === Moving Average Aggregation
 
-ifdef::asciidoctor[]
 deprecated:[6.4.0, "The Moving Average aggregation has been deprecated in favor of the more general <<search-aggregations-pipeline-movfn-aggregation,Moving Function Aggregation>>.  The new Moving Function aggregation provides all the same functionality as the Moving Average aggregation, but also provides more flexibility."]
-endif::[]
-ifndef::asciidoctor[]
-deprecated[6.4.0, The Moving Average aggregation has been deprecated in favor of the more general
-<<search-aggregations-pipeline-movfn-aggregation,Moving Function Aggregation>>.  The new Moving Function aggregation provides
-all the same functionality as the Moving Average aggregation, but also provides more flexibility.]
-endif::[]
 
 Given an ordered series of data, the Moving Average aggregation will slide a window across the data and emit the average
 value of that window.  For example, given the data `[1, 2, 3, 4, 5, 6, 7, 8, 9, 10]`, we can calculate a simple moving