Documentation: Remove reference to non-existing example plugins

Author: dschrempf

docs/contributing/plugin-tutorial.md

@@ -77,7 +77,6 @@ A plugin has a unique ID, a set of rules, a set of command handlers, and a set o
 The HLS codebase includes several plugins under the namespace `Ide.Plugin.*`, the most relevant are:
 
 - The `ghcide` plugin, which embeds `ghcide` as a plugin (`ghcide` is also the engine under HLS),
-- The `example` and `example2` plugins, offering a dubious welcome to new contributors,
 - The `ormolu`, `fourmolu`, `floskell` and `stylish-haskell` plugins, a testament to the code formatting wars of our community,
 - The `eval` plugin, a code lens provider to evaluate code in comments,
 - The `retrie` plugin, a code actions provider to execute retrie commands.