[fidl] Typo fixes.

TEST: No behavior change
Change-Id: I6e38871e6a912df62f0164990228b2b60baf4519
diff --git a/system/fidl/fuchsia-io/io.fidl b/system/fidl/fuchsia-io/io.fidl
index 7b3b5ba..f8ee51f 100644
--- a/system/fidl/fuchsia-io/io.fidl
+++ b/system/fidl/fuchsia-io/io.fidl
@@ -376,7 +376,7 @@
 [Layout = "Simple"]
 interface DirectoryAdmin : Directory {
     // Mount a channel representing a remote filesystem onto this directory.
-    // All future requests to this node will be forwarded to the remote filesytem.
+    // All future requests to this node will be forwarded to the remote filesystem.
     // To re-open a node without forwarding to the remote target, the node
     // should be opened with OPEN_FLAG_NO_RMOTE.
     Mount(Directory remote) -> (zx.status s);