Update docs/custom_detectors.md

Co-authored-by: sourcery-ai[bot] <58596630+sourcery-ai[bot]@users.noreply.github.com>

Author: RobGeada

docs/custom_detectors.md

@@ -1,6 +1,6 @@
 # Custom Detectors
 You can overwrite [custom_detectors.py](detectors/built_in/custom_detectors/custom_detectors.py) to create
-custom detectors in the built-in server based off of arbitrary Python code. This lets you quickly and flexible
+custom detectors in the built-in server based off of arbitrary Python code. This lets you quickly and flexibly
 create your own detection logic!
 
 The following rules apply: