Fix typo

Author: kgryte

spec/assumptions.md

@@ -49,7 +49,7 @@ namespace from array instances that are passed in, but not explicitly doing
 
 The assumption made during creation of this standard is that libraries are
 constrained by backwards compatibility guarantees to their users, and are
-likely unwilling to make significant bacwards-incompatible changes for the
+likely unwilling to make significant backwards-incompatible changes for the
 purpose of conforming to this standard. Therefore it is assumed that the
 standard will be made available in a new namespace within each library, or the
 library will provide a way to retrieve a module or module-like object that