Remove references to ExampleLintEngine from the documentation

Summary: See D9198.

Test Plan: eyeballed it

Reviewers: joshuaspence, btrahan

Reviewed By: btrahan

Subscribers: epriestley

Differential Revision: https://secure.phabricator.com/D9200

src/docs/user/userguide/arcanist_lint.diviner

@@ -335,7 +335,7 @@ file and uses it to decide which linters should be run on which paths. If no
 You can write a custom lint engine instead, which can make a more powerful set
 of decisions about which linters to run on which paths. For instructions on
 writing a custom lint engine, see @{article:Arcanist User Guide: Customizing
-Lint, Unit Tests and Workflows} and @{class@arcanist:ExampleLintEngine}.
+Lint, Unit Tests and Workflows}.
 
 To name an alternate lint engine, set `lint.engine` in your `.arcconfig` to the
 name of a class which extends @{class@arcanist:ArcanistLintEngine}. For more

src/docs/user/userguide/arcanist_lint_unit.diviner

@@ -87,7 +87,5 @@ This is mostly useful for debugging and testing.
 
 = Next Steps =
 
-  - Browse the source for an example lint engine at
-    @{class@arcanist:ExampleLintEngine}; or
-  - learn how to reuse existing linters by reading
+  - Learn how to reuse existing linters by reading
     @{article:Arcanist User Guide: Customizing Existing Linters}.