Update design/mvp/CanonicalABI.md

Co-authored-by: Luke Wagner <mail@lukewagner.name>

Author: sunfishcode

design/mvp/CanonicalABI.md

@@ -1459,7 +1459,7 @@ def mangle_instances(xs, path = ''):
 The three `TODO` cases are intended to be filled in by future PRs extending
 the Canonical ABI.
 
-#### Function and value type mangling
+#### Function type mangling
 
 Function and value types are recursively mangled into
 [`wit`](WIT.md)-compatible syntax: