[8.11](backport #3554) Remove unused APM attributes (#3566)

* remove unused attrs (#3554)

(cherry picked from commit 094640e)

# Conflicts:
#	docs/en/apm-server/version.asciidoc
#	docs/en/observability/apm.asciidoc

* Apply suggestions from code review

---------

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

docs/en/apm-server/version.asciidoc

@@ -1,10 +1,3 @@
-// doc-branch can be: master, 8.0, 8.1, etc.
-:doc-branch: master
-:go-version: 1.21.3
-:python: 3.7
-:docker: 1.12
-:docker-compose: 1.11
-
 include::{asciidoc-dir}/../../shared/versions/stack/{source_branch}.asciidoc[]
 
 // Agent link attributes