Raise minimum toolchain for the backtrace feature to 1.60

    error[E0658]: use of unstable library feature 'int_abs_diff'
       --> github.com-1ecc6299db9ec823/miniz_oxide-0.6.4/src/inflate/core.rs:824:54
        |
    824 |     if out_buf_size_mask == usize::MAX && source_pos.abs_diff(out_pos) == 1 && out_pos > source_pos {
        |                                                      ^^^^^^^^

    error[E0658]: use of unstable library feature 'int_abs_diff'
       --> github.com-1ecc6299db9ec823/miniz_oxide-0.6.4/src/inflate/core.rs:833:61
        |
    833 |     } else if out_buf_size_mask == usize::MAX && source_pos.abs_diff(out_pos) >= 4 && out_pos > source_pos {
        |                                                             ^^^^^^^^

.github/workflows/ci.yml

@@ -23,7 +23,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        rust: [nightly, beta, stable, 1.56.0]
+        rust: [nightly, beta, stable, 1.60.0]
     timeout-minutes: 45
     steps:
       - uses: actions/checkout@v3
@@ -53,8 +53,6 @@ jobs:
           components: rust-src
       - run: cargo check
       - run: cargo check --no-default-features
-      - run: cargo check --features backtrace
-        if: matrix.rust != '1.39.0' && matrix.rust != '1.50.0'
 
   windows:
     name: Windows