Fix link

analyzer-comments/crystal/two-fer/string_concatenation.md

@@ -1,6 +1,6 @@
 # string concatenation
 
-String concatenation is perfectly valid within Ruby, but a more common way to compose a string is with [string interpolation](http://ruby-for-beginners.rubymonstas.org/bonus/string_interpolation.html). For example:
+String concatenation is perfectly valid within Ruby, but a more common way to compose a string is with [string interpolation][interpolation]. For example:
 
 ```crystal
 # Rather than:
@@ -9,3 +9,5 @@ String concatenation is perfectly valid within Ruby, but a more common way to co
 # Consider:
 "One for #{name_variable}, one for me."
 ```
+
+[interpolation]: https://crystal-lang.org/reference/latest/syntax_and_semantics/literals/string.html#interpolation