fix(ruby): use hostType=rubygems for bundler env (#11196)

docs/usage/private-modules.md

@@ -119,7 +119,7 @@ The following details the most common/popular manager artifacts updating and how
 
 ### bundler
 
-`hostRules` with `hostType=bundler` are converted into environment variables which Bundler supports.
+`hostRules` with `hostType=rubygems` are converted into environment variables which Bundler supports.
 
 ### composer
 

lib/manager/bundler/artifacts.ts

@@ -125,7 +125,7 @@ export async function updateArtifacts(
     ];
 
     const bundlerHostRules = findAllAuthenticatable({
-      hostType: 'bundler',
+      hostType: 'rubygems',
     });
 
     const bundlerHostRulesVariables = bundlerHostRules.reduce(