Update call-built-in-actors.md

fix spelling

Author: robertagora

smart-contracts/developing-contracts/call-built-in-actors.md

@@ -1,7 +1,7 @@
 ---
 description: >-
   Filecoin built-in actors can be invoked in a smart contract using either the
-  Protocol API or the Zondax filecoin.solifity library. This page provides
+  Protocol API or the Filecoin.sol library. This page provides
   instructions on how to use each method.
 ---