Spell "compatibility" right

In the preceding commits (#15),
I consistently spelled "compatibility" wrong. Fix it.

Fixing the filename requires a cross-repo change (with this and
racket/racket#5434), so it'll be the second
cross-repo breaking change in ~3 hours, but it seems better to do it now than
wait until later or leave the misspelling there forever.

Sorry :(

Author: jesboat

compatibility-lib/mzscheme/main.rkt

@@ -222,7 +222,7 @@
                    force
                    promise?)
 
-             (only racket/private/for-compatability-lib
+             (only racket/private/for-compatibility-lib
                    define
                    define-for-syntax
                    define-syntax

compatibility-lib/mzscheme/private/stxmz-body.rkt

@@ -4,7 +4,7 @@
 (module stxmz-body '#%kernel
   ;; These could probably change to just be `(require racket/base)`.
   (#%require (only racket/base define-syntax)
-             (for-syntax '#%kernel racket/private/for-compatability-lib))
+             (for-syntax '#%kernel racket/private/for-compatibility-lib))
 
   ;; So that expansions print the way the Racket programmer expects:
   (#%require (rename '#%kernel #%plain-module-begin #%module-begin))