Fixing syntax for _any operator (#5403)

Author: tarunk2

docs/apm/traces/search-query-language-support-for-traces.md

@@ -39,7 +39,7 @@ A Keyword Search Expression defines the scope of data for the query. You need to
 
 In scenarios where users are not familiar with the schema and would like to search across all the fields, `_any` modifier provides a means to search for a specified value from all of the Ingest Time Fields in your data. For example, to search for data with any field that has a value of success you would put `_any=success` in the scope of your query.
 
-Syntax: `_any<value>`
+Syntax: `_any=<value>`
 
 The `_any` option is not supported outside of the scope of a query. This is supported for the Security and Tracing tiers.