[DOCS] Remove outdated APM ifeval (#81402) (#81439)

Removes the old `ifeval` for links to 7.x APM documentation. 7.x no longer exists, so this code isn't needed.

Originally added in #56538.

Co-authored-by: Brandon Morelli <brandon.morelli@elastic.co>

docs/Versions.asciidoc

@@ -59,12 +59,3 @@ Shared attribute values are pulled from elastic/docs
 ///////
 
 include::{docs-root}/shared/attributes.asciidoc[]
-
-///////
-APM does not build n.x documentation. Links from .x branches should point to master instead
-///////
-ifeval::["{source_branch}"=="7.x"]
-:apm-server-ref:       {apm-server-ref-m}
-:apm-server-ref-v:     {apm-server-ref-m}
-:apm-overview-ref-v:   {apm-overview-ref-m}
-endif::[]