Add 7.10 branch for APM books

Author: lcawl

conf.yaml

@@ -975,7 +975,7 @@ contents:
                 prefix:     get-started
                 index:      docs/guide/index.asciidoc
                 current:    *stackcurrent
-                branches:   [ master, 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 ]
+                branches:   [ master, 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
                 chunk:      1
                 tags:       APM Server/Reference
@@ -991,7 +991,7 @@ contents:
                 prefix:     server
                 index:      docs/index.asciidoc
                 current:    *stackcurrent
-                branches:   [ master, 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 ]
+                branches:   [ master, 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
                 chunk:      1
                 tags:       APM Server/Reference