Remove windows from CI

We don't actually look at the CI results for windows anyway!

In general, rust-analyzer should be written in a completely
OS-independent way. That is, testing on one OS should be enough. If
this is not the case, that means something is seriously broken.

No doubt there are components which actually talk to the outside
world, and they may be platform dependent. We should extract such
components to a separate repo with an extensive multi platform CI,
like we did for VFS

.travis.yml

@@ -4,43 +4,36 @@ before_cache:
     - rm -fr ./target/debug/{deps,.fingerprint}/{*ra_*,*test*,*tools*,*gen_lsp*,*thread_worker*}
     - rm -f  ./target/.rustc_info.json
 
-build: &rust_build
-    language: rust
-    rust: stable
-    script:
-        - rustup component add rustfmt
-        - rustup component add rust-src
-        - cargo test --no-run  # let's measure compile time separately
-        - cargo test
-        - cargo doc --all --no-deps
-    env:
-        - RUSTFLAGS="-D warnings", CARGO_INCREMENTAL=0
-
 matrix:
     include:
         - os: linux
-          before_script:
+          language: rust
+          rust: stable
+          script:
+              - rustup component add rustfmt
+              - rustup component add rust-src
+              - cargo test --no-run  # let's measure compile time separately
+              - cargo test
+          env:
+              - RUSTFLAGS="-D warnings", CARGO_INCREMENTAL=0
+
+        - os: linux
+          if: branch = master AND type = push
+          before_stript:
               - DEPLOY_DOCS=1
-          <<: *rust_build
+          language: rust
+          rust: stable
+          script:
+              - cargo doc --all --no-deps
+          env:
+              - RUSTFLAGS="-D warnings", CARGO_INCREMENTAL=0
+
         - language: node_js
           node_js: node
           before_script: false
           script:
               - cd editors/code && npm ci && npm run travis
 
-        - os: windows
-          if: branch = master AND type = push
-          before_script:
-              - dos2unix ./crates/ra_syntax/tests/data/parser/**/*.txt
-              - dos2unix ./crates/ra_syntax/tests/data/parser/**/*.rs
-          <<: *rust_build
-
-    allow_failures:
-        # Because Travis-Windows-Rust can be flaky
-        # We still support Windows and want the tests to be succeeding,
-        # but there are too many spurious failures
-        - os: windows
-
 branches:
     only:
         - staging