update method signature for hash update to be consistent with the docs
diff --git a/cryptography/primitives/hashes.py b/cryptography/primitives/hashes.py
index a87d09e..e8c1f92 100644
--- a/cryptography/primitives/hashes.py
+++ b/cryptography/primitives/hashes.py
@@ -29,8 +29,8 @@
         self._api = api
         self._ctx = self._api.create_hash_context(self) if ctx is None else ctx
 
-    def update(self, string):
-        self._api.update_hash_context(self._ctx, string)
+    def update(self, data):
+        self._api.update_hash_context(self._ctx, data)
 
     def copy(self):
         return self.__class__(ctx=self._copy_ctx())