Update to syn 2

test_suite/tests/ui/malformed/cut_off.stderr

@@ -1,4 +1,4 @@
-error: unexpected end of input, expected literal
+error: unexpected end of input, expected an expression
  --> tests/ui/malformed/cut_off.rs:4:17
   |
 4 | #[serde(rename =)]

test_suite/tests/ui/malformed/not_list.stderr

@@ -1,11 +1,11 @@
-error: expected #[serde(...)]
+error: expected attribute arguments in parentheses: #[serde(...)]
  --> tests/ui/malformed/not_list.rs:4:3
   |
 4 | #[serde]
   |   ^^^^^
 
-error: expected #[serde(...)]
- --> tests/ui/malformed/not_list.rs:5:3
+error: expected parentheses: #[serde(...)]
+ --> tests/ui/malformed/not_list.rs:5:9
   |
 5 | #[serde = "?"]
-  |   ^^^^^^^^^^^
+  |         ^

test_suite/tests/ui/unexpected-literal/container.stderr

@@ -1,4 +1,4 @@
-error: unexpected literal in serde container attribute
+error: expected path
  --> tests/ui/unexpected-literal/container.rs:4:9
   |
 4 | #[serde("literal")]

test_suite/tests/ui/unexpected-literal/field.stderr

@@ -1,4 +1,4 @@
-error: unexpected literal in serde field attribute
+error: expected path
  --> tests/ui/unexpected-literal/field.rs:5:13
   |
 5 |     #[serde("literal")]

test_suite/tests/ui/unexpected-literal/variant.stderr

@@ -1,4 +1,4 @@
-error: unexpected literal in serde variant attribute
+error: expected path
  --> tests/ui/unexpected-literal/variant.rs:5:13
   |
 5 |     #[serde("literal")]