Fix a typo

Author: koic

README.adoc

@@ -2951,7 +2951,7 @@ def set_x(x) = (@x = x)
 def print_foo = puts("foo")
 ----
 
-=== Ambiguous Endless Method Definitions [[ambiguous-endless-method-defintions]]
+=== Ambiguous Endless Method Definitions [[ambiguous-endless-method-definitions]]
 
 Keywords with lower precedence than `=` can appear ambiguous when used after an endless method definition. This includes `and`, `or`, and the modifier forms of `if`, `unless`, `while`, and `until`. In these cases, the code may appear to include these keywords as part of the method body, but instead they actually modify the method definition itself.