THRIFT-5600: upgrade rust toolchain to 1.61 and edition 2021
THRIFT-5606: Wrong indent for const double
Client: rs
Patch: Ommy Zhang <tdxdxoz@gmail.com>

This closes #2634
diff --git a/build/docker/ubuntu-xenial/Dockerfile b/build/docker/ubuntu-xenial/Dockerfile
index aec9bd3..34e902e 100644
--- a/build/docker/ubuntu-xenial/Dockerfile
+++ b/build/docker/ubuntu-xenial/Dockerfile
@@ -249,7 +249,7 @@
       ruby-bundler
 
 # Rust dependencies
-RUN curl https://sh.rustup.rs -sSf | sh -s -- --default-toolchain 1.40.0 -y
+RUN curl https://sh.rustup.rs -sSf | sh -s -- --default-toolchain 1.61.0 -y
 
 # Locale(s) for cpp unit tests
 RUN apt-get install -y --no-install-recommends \