Revert "fix(es/transform/compat): Preserve more span (#2766)"

This reverts commit ddfc7e6.

crates/swc_ecma_transforms_compat/src/es2017/async_to_generator.rs

@@ -1,5 +1,5 @@
 use std::{iter, mem::replace};
-use swc_common::{util::take::Take, BytePos, Mark, Span, Spanned, SyntaxContext, DUMMY_SP};
+use swc_common::{util::take::Take, Mark, Span, Spanned, DUMMY_SP};
 use swc_ecma_ast::*;
 use swc_ecma_transforms_base::{helper, perf::Check};
 use swc_ecma_transforms_macros::fast_path;
@@ -429,28 +429,9 @@ impl VisitMut for Actual {
             })
         };
 
-        let func_span_lo = {
-            let key_span_lo = match &prop.key {
-                PropName::Ident(ident) => ident.span().lo(),
-                PropName::Str(str) => str.span().lo(),
-                PropName::Num(num) => num.span().lo(),
-                PropName::Computed(computed) => computed.span().lo(),
-                PropName::BigInt(bigint) => bigint.span().lo(),
-            };
-
-            // sub length of "async " from prop's key span
-            key_span_lo - BytePos(6)
-        };
-
-        let func_span = Span::new(
-            func_span_lo,
-            func_span_lo + BytePos(1), // dummy pos
-            SyntaxContext::empty(),
-        );
-
         prop.function = Function {
             params: original_fn_params,
-            span: func_span,
+            span: prop_method_span,
             is_async: false,
             is_generator: false,
             body: Some(BlockStmt {