[rust]: remove vecdeque_binary_search feature

backend/rust-toolchain

@@ -0,0 +1,2 @@
+[toolchain]
+channel = "nightly-2021-04-24"

frontend/rust-lib/flowy-document/src/lib.rs

@@ -1,5 +1,3 @@
-#![feature(vecdeque_binary_search)]
-
 pub mod errors;
 pub mod module;
 mod notify;