revert vrl compiler changes

Signed-off-by: Vladimir Zhuk <vladimir.zhuk@datadoghq.com>

lib/vrl/compiler/src/lib.rs

@@ -48,6 +48,6 @@ pub fn compile_with_state(
 
 /// re-export of commonly used parser types.
 pub(crate) mod parser {
-    pub use ::parser::ast::{self, AssignmentOp, AssignmentTarget, Ident, Node};
+    pub use ::parser::ast::{self, Ident, Node};
     pub use ::parser::Program;
 }