docs(manager/bundler): rewrite (#31330)

lib/modules/manager/bundler/readme.md

@@ -1,8 +1,14 @@
-The `bundler` manager is used to extract dependencies from `Gemfile` and `Gemfile.lock` files.
+Renovate uses the `bundler` manager to extract dependencies from `Gemfile` and `Gemfile.lock` files.
 
 ### Authenticating private registry
 
-If you need Bundler to authenticate with a private registry - and it's not the same host as your GitHub/GitLab/etc - then you should do so with `hostRules` and be sure to set the `hostType`. e.g.
+If:
+
+- you need Bundler to authenticate to a private registry
+- _and_ that private registry is _not_ on the same host as Renovate (your GitHub/GitLab/etc)
+
+Then you should authenticate Renovate with `hostRules`.
+For example:
 
 ```json
 {
@@ -16,17 +22,13 @@ If you need Bundler to authenticate with a private registry - and it's not the s
 }
 ```
 
-Important notes regarding the above:
-
-`hostType` is a required field, and you must provide a value.
-If you use Renovate `v26` or higher, set `hostType=rubygems`.
-If you use Renovate `v25` or lower, set `hostType=bundler`.
-
-If the registry is used for multiple package types then you may need multiple `hostRules`.
+Important notes:
 
-Instead of `token`, you may also supply `username` and `password` instead.
+- `hostType` is a required field, set `hostType=rubygems`
+- If you use the same registry for more than one package type, you may need more than one `hostRules` entry
+- Instead of `token`, you can use a `username` and `password`
 
-If you don't want to commit raw secrets to your repository, either:
+To avoid committing raw secrets to your repository, either:
 
-- If self hosting, add the `hostRules` to your bot's configuration file rather than the repository's configuration file, or
-- If using the Mend Renovate App, make use of the [`encrypted`](../../../configuration-options.md#encrypted) capability
+- If self-hosting: add the `hostRules` to your bot config file, instead of the repository configuration file, or
+- If using the Mend Renovate App: use the [`encrypted`](../../../configuration-options.md#encrypted) config option