rename yellow -> syntax_node

why yellow in the first place? Its red + green.

crates/ra_syntax/src/yellow/builder.rs

@@ -1,41 +0,0 @@
-use crate::{
-    parser_impl::Sink,
-    yellow::{GreenNode, RaTypes, SyntaxError},
-    SmolStr, SyntaxKind,
-};
-use rowan::GreenNodeBuilder;
-
-pub(crate) struct GreenBuilder {
-    errors: Vec<SyntaxError>,
-    inner: GreenNodeBuilder<RaTypes>,
-}
-
-impl GreenBuilder {
-    pub(crate) fn new() -> GreenBuilder {
-        GreenBuilder { errors: Vec::new(), inner: GreenNodeBuilder::new() }
-    }
-}
-
-impl Sink for GreenBuilder {
-    type Tree = (GreenNode, Vec<SyntaxError>);
-
-    fn leaf(&mut self, kind: SyntaxKind, text: SmolStr) {
-        self.inner.leaf(kind, text);
-    }
-
-    fn start_branch(&mut self, kind: SyntaxKind) {
-        self.inner.start_internal(kind)
-    }
-
-    fn finish_branch(&mut self) {
-        self.inner.finish_internal();
-    }
-
-    fn error(&mut self, error: SyntaxError) {
-        self.errors.push(error)
-    }
-
-    fn finish(self) -> (GreenNode, Vec<SyntaxError>) {
-        (self.inner.finish(), self.errors)
-    }
-}