Remove unneeded dependencies from Install/Upgrade Guide (#2760)

**Problem:**
With elastic/stack-docs#2495, the [Elastic Installation and Upgrade Guide](https://www.elastic.co/guide/en/elastic-stack/current/index.html) no longer requires dependencies for several repos in 8.9+ branches.

**Solution:**
Remove the dependencies from the docs build config.

conf.yaml

@@ -159,34 +159,34 @@ contents:
               -
                 repo:   apm-server
                 path:   docs/
-                exclude_branches:   [ 6.8, 6.7, 6.6, 6.5, 6.4, 6.3, 6.2, 6.1, 6.0, 5.6, 5.5, 5.4, 5.3, 5.2, 5.1, 5.0 ]
+                exclude_branches:   [ main, 8.10, 8.9, 6.8, 6.7, 6.6, 6.5, 6.4, 6.3, 6.2, 6.1, 6.0, 5.6, 5.5, 5.4, 5.3, 5.2, 5.1, 5.0 ]
               -
                 repo:   beats
                 path:   libbeat/docs
-                exclude_branches:   [ 6.8, 6.7, 6.6, 6.5, 6.4, 6.3, 6.2, 6.1, 6.0, 5.6, 5.5, 5.4, 5.3, 5.2, 5.1, 5.0 ]
+                exclude_branches:   [ main, 8.10, 8.9, 6.8, 6.7, 6.6, 6.5, 6.4, 6.3, 6.2, 6.1, 6.0, 5.6, 5.5, 5.4, 5.3, 5.2, 5.1, 5.0 ]
               -
                 repo:   elasticsearch
                 path:   docs/
               -
                 repo:   elasticsearch-hadoop
                 path:   docs/src/reference/asciidoc
-                exclude_branches:   [ 6.8, 6.7, 6.6, 6.5, 6.4, 6.3, 6.2, 6.1, 6.0, 5.6, 5.5, 5.4, 5.3, 5.2, 5.1, 5.0 ]
+                exclude_branches:   [ main, 8.10, 8.9, 6.8, 6.7, 6.6, 6.5, 6.4, 6.3, 6.2, 6.1, 6.0, 5.6, 5.5, 5.4, 5.3, 5.2, 5.1, 5.0 ]
               -
                 repo:   security-docs
                 path:   docs/
-                exclude_branches:   [ 7.17, 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, 5.6, 5.5, 5.4, 5.3, 5.2, 5.1, 5.0 ]
+                exclude_branches:   [ main, 8.10, 8.9, 7.17, 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, 5.6, 5.5, 5.4, 5.3, 5.2, 5.1, 5.0 ]
               -
                 repo:   kibana
                 path:   docs/
-                exclude_branches:   [ 6.8, 6.7, 6.6, 6.5, 6.4, 6.3, 6.2, 6.1, 6.0, 5.6, 5.5, 5.4, 5.3, 5.2, 5.1, 5.0 ]
+                exclude_branches:   [ main, 8.10, 8.9, 6.8, 6.7, 6.6, 6.5, 6.4, 6.3, 6.2, 6.1, 6.0, 5.6, 5.5, 5.4, 5.3, 5.2, 5.1, 5.0 ]
               -
                 repo:   logstash
                 path:   docs/
-                exclude_branches:   [ 6.8, 6.7, 6.6, 6.5, 6.4, 6.3, 6.2, 6.1, 6.0, 5.6, 5.5, 5.4, 5.3, 5.2, 5.1, 5.0 ]
+                exclude_branches:   [ main, 8.10, 8.9, 6.8, 6.7, 6.6, 6.5, 6.4, 6.3, 6.2, 6.1, 6.0, 5.6, 5.5, 5.4, 5.3, 5.2, 5.1, 5.0 ]
               -
                 repo:   observability-docs
                 path:   docs/en/observability
-                exclude_branches:   [ 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, 5.6, 5.5, 5.4, 5.3, 5.2, 5.1, 5.0 ]
+                exclude_branches:   [ main, 8.10, 8.9, 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, 5.6, 5.5, 5.4, 5.3, 5.2, 5.1, 5.0 ]
               -
                 repo:   docs
                 path:   shared/versions/stack/{version}.asciidoc