Don't duplicate line numbers when annotating internal errors

Closes 5463

The `annotate_snippets` crate adds line number and column info to the
output, so we don't need to append the line number to the `origin`.

Previously, internal errors would be output with the line number twice.
See how 478 is duplicated in the example below.

```
error[internal]: line formatted, but exceeded maximum width
   --> /path/to/file.rs:478:478:101
```

Now the line number is not duplicated.

```
error[internal]: line formatted, but exceeded maximum width
   --> /path/to/file.rs:478:101
```

src/format_report_formatter.rs

@@ -78,7 +78,7 @@ impl<'a> Display for FormatReportFormatter<'a> {
                     None
                 };
 
-                let origin = format!("{}:{}", file, error.line);
+                let origin = file.to_string();
                 let slice = Slice {
                     source: &error.line_buffer.clone(),
                     line_start: error.line,

src/formatting.rs

@@ -645,3 +645,32 @@ where
         f();
     }
 }
+
+#[cfg(test)]
+mod test {
+    use std::path::PathBuf;
+
+    use crate::FormatReportFormatterBuilder;
+
+    use super::*;
+
+    #[test]
+    fn test_internal_error_file_and_line_number_annotations() {
+        let mut config = Config::default();
+        config.set().error_on_unformatted(true);
+
+        let mut text = String::new();
+        text.push_str("fn main() {\n");
+        text.push_str("    println!(\"hello world!\"); \n"); // Note the space before the '\n'
+        text.push_str("}");
+
+        let report = FormatReport::new();
+        let name = FileName::Real(PathBuf::from("internal_error_test.rs"));
+
+        format_lines(&mut text, &name, &vec![], &config, &report);
+        let output = FormatReportFormatterBuilder::new(&report)
+            .build()
+            .to_string();
+        assert!(output.contains("--> internal_error_test.rs:2:30"));
+    }
+}