Rust: fix a name conflict when building with "no_std" feature (#7268)

* Fix a name conflict when building with "no_std" feature

* Bump patch version

rust/flatbuffers/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "flatbuffers"
-version = "2.1.1"
+version = "2.1.2"
 edition = "2018"
 authors = ["Robert Winslow <hello@rwinslow.com>", "FlatBuffers Maintainers"]
 license = "Apache-2.0"

rust/flatbuffers/src/verifier.rs

@@ -6,7 +6,8 @@ use crate::follow::Follow;
 use crate::{ForwardsUOffset, SOffsetT, SkipSizePrefix, UOffsetT, VOffsetT, Vector, SIZE_UOFFSET};
 
 #[cfg(feature="no_std")]
-extern crate thiserror_core2 as thiserror;
+use thiserror_core2::Error;
+#[cfg(not(feature="no_std"))]
 use thiserror::Error;
 
 /// Traces the location of data errors. Not populated for Dos detecting errors.