Fix format of markdown query help files

ruby/ql/src/queries/variables/UninitializedLocal.md

@@ -1,6 +1,4 @@
-# Method call on `nil`
-
-## Description
+## Overview
 In Ruby, it is not necessary to explicitly initialize variables.
 If a local variable has not been explicitly initialized, it will have the value `nil`. If this happens unintentionally, though, the variable will not represent an object with the expected methods, and a method call on the variable will raise a `NoMethodError`.
 
@@ -11,7 +9,7 @@ This can be achieved by using a safe navigation or adding a check for `nil`.
 
 Note: You do not need to explicitly initialize the variable, if you can make the program deal with the possible `nil` value. In particular, initializing the variable to `nil` will have no effect, as this is already the value of the variable. If `nil` is the only possible default value, you need to handle the `nil` value instead of initializing the variable.
 
-## Examples
+## Example
 
 In the following code, the call to `create_file` may fail and then the call `f.close` will raise a `NoMethodError` since `f` will be `nil` at that point.
 
@@ -38,4 +36,3 @@ end
 
 - https://www.rubyguides.com/: [Nil](https://www.rubyguides.com/2018/01/ruby-nil/)
 - https://ruby-doc.org/: [NoMethodError](https://ruby-doc.org/core-2.6.5/NoMethodError.html)
-