Stop building APM Server and Overview books

conf.yaml

@@ -1119,9 +1119,9 @@ contents:
               - title:      APM Overview
                 prefix:     get-started
                 index:      docs/guide/index.asciidoc
-                current:    *stackcurrent
-                branches:   [ master, 8.0, 7.16, 7.15, 7.14, 7.13, 7.12, 7.11, 7.10, 7.9, 7.8, 7.7, 7.6, 7.5, 7.4, 7.3, 7.2, 7.1, 7.0, 6.8, 6.7, 6.6, 6.5, 6.4, 6.3, 6.2, 6.1, 6.0 ]
-                live:       *stacklive
+                current:    7.15
+                branches:   [ 7.15, 7.14, 7.13, 7.12, 7.11, 7.10, 7.9, 7.8, 7.7, 7.6, 7.5, 7.4, 7.3, 7.2, 7.1, 7.0, 6.8, 6.7, 6.6, 6.5, 6.4, 6.3, 6.2, 6.1, 6.0 ]
+                live:       [ 7.15, 6.8 ]
                 chunk:      1
                 tags:       APM Server/Reference
                 subject:    APM
@@ -1135,9 +1135,9 @@ contents:
               - title:      APM Server Reference
                 prefix:     server
                 index:      docs/index.asciidoc
-                current:    *stackcurrent
-                branches:   [ master, 8.0, 7.16, 7.15, 7.14, 7.13, 7.12, 7.11, 7.10, 7.9, 7.8, 7.7, 7.6, 7.5, 7.4, 7.3, 7.2, 7.1, 7.0, 6.8, 6.7, 6.6, 6.5, 6.4, 6.3, 6.2, 6.1, 6.0 ]
-                live:       *stacklive
+                current:    7.15
+                branches:   [ 7.15, 7.14, 7.13, 7.12, 7.11, 7.10, 7.9, 7.8, 7.7, 7.6, 7.5, 7.4, 7.3, 7.2, 7.1, 7.0, 6.8, 6.7, 6.6, 6.5, 6.4, 6.3, 6.2, 6.1, 6.0 ]
+                live:       [ 7.15, 6.8 ]
                 chunk:      1
                 tags:       APM Server/Reference
                 subject:    APM