[UG] Fix typo causing Sphinx warning "Title overline too short"

LittleJ · LittleJ · commit b890d67d553d · 2020-02-24T21:10:21.000+01:00
diff --git a/user_guide_src/source/testing/overview.rst b/user_guide_src/source/testing/overview.rst
@@ -10,9 +10,9 @@ helper methods to make testing every aspect of your application as painless as p
     :local:
     :depth: 2
 
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+*************
 System Set Up
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+*************
 
 Installing phpUnit
 ==================
