Silence expected parser error

I find otherwise the test output can be a bit noisy, and in particular
the error messages make me think some test somewhere failed when even
when it's all passing.

Author: matthewhughes934

src/test/mod.rs

@@ -534,7 +534,9 @@ fn stdin_parser_panic_caught() {
     // See issue #3239.
     for text in ["{", "}"].iter().cloned().map(String::from) {
         let mut buf = vec![];
-        let mut session = Session::new(Default::default(), Some(&mut buf));
+        let mut config = Config::default();
+        config.set().show_parse_errors(false);
+        let mut session = Session::new(config, Some(&mut buf));
         let _ = session.format(Input::Text(text));
 
         assert!(session.has_parsing_errors());

tests/parser/issue-4126/lib.rs

@@ -1 +1,3 @@
+// rustfmt-show_parse_errors: false
+
 mod invalid;

tests/parser/issue_4418.rs

@@ -1 +1,3 @@
-}
+// rustfmt-show_parse_errors: false
+
+}

tests/parser/stashed-diag.rs

@@ -1,3 +1,5 @@
+// rustfmt-show_parse_errors: false
+
 #![u={static N;}]
 
 fn main() {}

tests/parser/stashed-diag2.rs

@@ -1,3 +1,5 @@
+// rustfmt-show_parse_errors: false
+
 trait Trait<'1> { s> {}
 
 fn main() {}

tests/parser/unclosed-delims/issue_4466.rs

@@ -1,3 +1,5 @@
+// rustfmt-show_parse_errors: false
+
 fn main() {
     if true {
         println!("answer: {}", a_func();
@@ -8,4 +10,4 @@ fn main() {
 
 fn a_func() -> i32 {
     42
-} 
+}