Raise rustc required for backtrace feature to 1.67

Required by recent versions of the cc crate.

    error: package `cc v1.0.106` cannot be built because it requires rustc 1.67 or newer, while the currently active rustc version is 1.65.0
    Either upgrade to rustc 1.67 or newer, or use
    cargo update -p cc@1.0.106 --precise ver
    where `ver` is the latest version of `cc` supporting rustc 1.65.0

.github/workflows/ci.yml

@@ -50,7 +50,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        rust: [1.65.0, 1.52.0, 1.51.0, 1.50.0, 1.39.0]
+        rust: [1.67.0, 1.65.0, 1.52.0, 1.51.0, 1.50.0, 1.39.0]
     timeout-minutes: 45
     steps:
       - uses: actions/checkout@v4
@@ -61,7 +61,7 @@ jobs:
       - run: cargo check
       - run: cargo check --no-default-features
       - run: cargo check --features backtrace
-        if: matrix.rust != '1.52.0' && matrix.rust != '1.51.0' && matrix.rust != '1.50.0' && matrix.rust != '1.39.0'
+        if: matrix.rust != '1.65.0' && matrix.rust != '1.52.0' && matrix.rust != '1.51.0' && matrix.rust != '1.50.0' && matrix.rust != '1.39.0'
 
   minimal:
     name: Minimal versions