rust: Update MSRV to 1.52

The bump of minimum rust version is required by some of the updated dependencies.

Closes #2802.

.github/workflows/rust-tests.yml

@@ -13,7 +13,7 @@ jobs:
       matrix:
         rust:
           # MSRV; most not be higher than the clippy rust version in checks.yml
-          - "1.47"
+          - "1.52"
           - "stable"
         os:
           - ubuntu-latest

rust/lib/src/lib.rs

@@ -1,5 +1,4 @@
-// Not compatible with the MSRV
-// #![warn(unsafe_op_in_unsafe_fn)]
+#![warn(unsafe_op_in_unsafe_fn)]
 #![allow(unused_unsafe)]
 // Not working yet in stable - https://github.com/rust-lang/rust-clippy/issues/8020
 // #![warn(clippy::undocumented_unsafe_blocks)]

rust/taskchampion/src/lib.rs

@@ -39,9 +39,9 @@ Users can define their own server impelementations.
 See the [TaskChampion Book](http://taskchampion.github.com/taskchampion)
 for more information about the design and usage of the tool.
 
-# Minimum Supported Rust Version
+# Minimum Supported Rust Version (MSRV)
 
-This crate supports Rust version 1.47 and higher.
+This crate supports Rust version 1.52 and higher.
 
  */