fix typo

doc/spec/tour.kk.md

@@ -1988,7 +1988,7 @@ The `tail` keyword guarantees that a function is tail-recursive. These functions
 The `fbip` keyword guarantees that a function is optimized by the compiler to use in-place mutation when possible.
 However, unlike `fip`, `fbip` allows for deallocation, and also allows for non tail calls, which means these functions can use non-constant stack space.
 
-Both `fip` and `fbip` can allow for a constant amount of allocation using `fib(n)` or `fib(n)` where `n` is the number of constructor allocations allowed.
+Both `fip` and `fbip` can allow for a constant amount of allocation using `fip(n)` or `fbip(n)` where `n` is the number of constructor allocations allowed.
 This allows them to be used in insertion functions for datastructures, where at least one constructor for the inserted element is necessary.
 
 Following are a few examples of the techniques of FBIP in action.