Remove minimal versions build from Windows

Looks like minimal versions don't work with the 0.6.5 release of `rand`
on Windows...

appveyor.yml

@@ -2,16 +2,12 @@ environment:
   matrix:
   - TARGET: x86_64-pc-windows-msvc
     OTHER_TARGET: i686-pc-windows-msvc
-  - TARGET: x86_64-pc-windows-msvc
-    MINIMAL_VERSIONS: true
-    CFG_DISABLE_CROSS_TESTS: 1
 
 install:
   - if NOT defined APPVEYOR_PULL_REQUEST_NUMBER if "%APPVEYOR_REPO_BRANCH%" == "master" appveyor exit
   - appveyor-retry appveyor DownloadFile https://win.rustup.rs/ -FileName rustup-init.exe
   - rustup-init.exe -y --default-host x86_64-pc-windows-msvc --default-toolchain nightly
   - set PATH=%PATH%;C:\Users\appveyor\.cargo\bin
-  - if defined MINIMAL_VERSIONS rustup toolchain install 1.31.0
   - if defined OTHER_TARGET rustup target add %OTHER_TARGET%
   - rustc -V
   - cargo -V
@@ -22,8 +18,4 @@ clone_depth: 1
 build: false
 
 test_script:
-  # we don't have ci time to run the full `cargo test` with `minimal-versions` like
-  # - if defined MINIMAL_VERSIONS cargo +nightly generate-lockfile -Z minimal-versions && cargo +stable test
-  # so we just run `cargo check --tests` like
-  - if defined MINIMAL_VERSIONS cargo +nightly generate-lockfile -Z minimal-versions && cargo +1.31.0 check --tests --features=deny-warnings
-  - if NOT defined MINIMAL_VERSIONS cargo test --features=deny-warnings
+  - cargo test --features=deny-warnings