message: Update MSRVs of awint and rug
diff: @@ -53,8 +53,8 @@ table offers a brief comparison to a few alternatives.
  | Crate | License | Min rustc | Implementation | Features |
  | :--------------- | :------------- | :-------- | :------------- | :------- |
  | **`num-bigint`** | MIT/Apache-2.0 | 1.31 | pure rust | dynamic width, number theoretical functions |
  -| [`rug`] | LGPL-3.0+ | 1.37 | bundles [GMP] via [`gmp-mpfr-sys`] | all the features of GMP, MPFR, and MPC |
  -| [`awint`] | MIT/Apache-2.0 | 1.61 | pure rust | fixed width, heap or stack, concatenation macros |
  +| [`rug`] | LGPL-3.0+ | 1.65 | bundles [GMP] via [`gmp-mpfr-sys`] | all the features of GMP, MPFR, and MPC |
  +| [`awint`] | MIT/Apache-2.0 | 1.66 | pure rust | fixed width, heap or stack, concatenation macros |
  | [`bnum`] | MIT/Apache-2.0 | 1.61 | pure rust | fixed width, parity with Rust primitives including floats |
  | [`ibig`] | MIT/Apache-2.0 | 1.49 | pure rust | dynamic width, number theoretical functions |
  | [`crypto-bigint`] | MIT/Apache-2.0 | 1.57 | pure rust | fixed width, stack only |
  