Add rustup update to the workflow to update rustc to the latest version.

Otherwise integration tests fail due to problems with the test output in versions of the Rust test harness prior to 1.66. Currently Github installs 1.65 by default.

Also added a note to the README.md file to suggest using Rust 1.66 or later, since earlier versions have problems with assertion failure output.

PiperOrigin-RevId: 497359964

Author: hovinenb

.github/workflows/ci.yml

@@ -16,6 +16,8 @@ jobs:
 
     steps:
     - uses: actions/checkout@v3
+    - name: Update to latest Rust version
+      run: rustup update
     - name: Build
       run: cargo build --verbose
     - name: Run tests

README.md

@@ -11,6 +11,9 @@ This library brings the rich assertion types of Google's C++ testing library
  * A new set of assertion macros offering similar functionality to those of
    [GoogleTest](https://google.github.io/googletest/primer.html#assertions).
 
+**We recommend using Rust 1.66 or later with this library.** It does not work
+smoothly with prior versions.
+
 > :warning: The API is not fully stable and may still be changed until we
 > publish version 1.0.