Fix typo in CHANGELOG.

CHANGELOG.md

@@ -17,7 +17,7 @@ With this release, we dropped support for Coq 8.9.
   `frac_auth_agreeL` to `frac_auth_agree_L`, and
   `ufrac_auth_agreeL` to `ufrac_auth_agree_L`.
 * Add constructions to define a camera through restriction of the validity predicate
-  (`iso_cmra_mixin_restrict`) and through an isomophism (`iso_cmra_mixin`).
+  (`iso_cmra_mixin_restrict`) and through an isomorphism (`iso_cmra_mixin`).
 * Add a `frac_agree` library which encapsulates `frac * agree A` for some OFE
   `A`, and provides some useful lemmas.