Fix strange error on unbalanced curly braces (#8906)

# Description

Fixes issue https://github.com/nushell/nushell/issues/8400 

# User-Facing Changes

Before

![image](https://user-images.githubusercontent.com/5063945/232443913-a8fe9f50-2014-4edd-95b0-516058566f64.png)

After

![image](https://user-images.githubusercontent.com/5063945/232444266-375d9438-0688-4f49-a884-b8650110f7fe.png)

crates/nu-parser/src/lex.rs

@@ -191,7 +191,7 @@ pub fn lex_item(
                     Some(ParseError::Unbalanced(
                         "{".to_string(),
                         "}".to_string(),
-                        Span::new(span.end, span.end),
+                        Span::new(span.end, span.end + 1),
                     )),
                 );
             }

src/tests/test_parser.rs

@@ -488,6 +488,11 @@ fn unbalanced_delimiter3() -> TestResult {
     fail_test(r#"{"#, "Unexpected end of code")
 }
 
+#[test]
+fn unbalanced_delimiter4() -> TestResult {
+    fail_test(r#"}"#, "unbalanced { and }")
+}
+
 #[test]
 fn register_with_string_literal() -> TestResult {
     fail_test(r#"register 'nu-plugin-math'"#, "File not found")