Fix #4052

The bug actually had two instances:
- Callback routes with literal matches and HTTP verbs has never worked
- The reported issue in #4052, which is a regression introduced in 3.0.1
  with abc299b3a234eb7da1b7e3d257b7eba2da649219

Removed the literal matches logic altogether to avoid similar issues
in the future and reduce code complexity. The same logic is performed
with the regular expressions logic.
diff --git a/user_guide_src/source/changelog.rst b/user_guide_src/source/changelog.rst
index 971a234..061efe8 100644
--- a/user_guide_src/source/changelog.rst
+++ b/user_guide_src/source/changelog.rst
@@ -15,6 +15,7 @@
 -------------------
 
 -  Fixed a bug (#2284) - :doc:`Database <database/index>` method ``protect_identifiers()`` breaks when :doc:`Query Builder <database/query_builder>` isn't enabled.
+-  Fixed a bug (#4052) - :doc:`Routing <general/routing>` with anonymous functions didn't work for routes that don't use regular expressions.
 
 Version 3.0.1
 =============