[Lint][Clippy] remove clippy ignore

[benjaminch]

Remove clippy -A clippy::multiple-crate-versions in https://github.com/benjaminch/miradors/blob/dev/.github/workflows/rust.yml#L27

Once steffengy/schannel-rs#82 will be merged

error: multiple versions for dependency `windows-sys`: 0.36.1, 0.42.0
  |
  = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#multiple_crate_versions
  = note: `-D clippy::multiple-crate-versions` implied by `-D warnings`

error: multiple versions for dependency `windows_aarch64_msvc`: 0.36.1, 0.42.0
  |
  = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#multiple_crate_versions

error: multiple versions for dependency `windows_i686_gnu`: 0.36.1, 0.42.0
  |
  = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#multiple_crate_versions

error: multiple versions for dependency `windows_i686_msvc`: 0.36.1, 0.42.0
  |
  = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#multiple_crate_versions

error: multiple versions for dependency `windows_x86_64_gnu`: 0.36.1, 0.42.0
  |
  = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#multiple_crate_versions

error: multiple versions for dependency `windows_x86_64_msvc`: 0.36.1, 0.42.0
  |
  = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#multiple_crate_versions

error: could not compile `miradors` due to 6 previous errors