Move respect accept header on no handler to 6.3.1

This commit moves the changelog entry for the change to respect the
accept header on no handler from the 7.0.0 section of the docs to 6.3.1.

Author: jasontedor

docs/CHANGELOG.asciidoc

@@ -107,7 +107,6 @@ ones that the user is authorized to access in case field level security is enabl
 Fixed prerelease version of elasticsearch in the `deb` package to sort before GA versions
 ({pull}29000[#29000])
 
-Respect accept header on requests with no handler ({pull}30383[#30383])
 Rollup::
 * Validate timezone in range queries to ensure they match the selected job when
 searching ({pull}30338[#30338])
@@ -211,6 +210,8 @@ coming[6.3.1]
 
 Reduce the number of object allocations made by {security} when resolving the indices and aliases for a request ({pull}30180[#30180])
 
+Respect accept header on requests with no handler ({pull}30383[#30383])
+
 //[float]
 //=== Regressions