fix: Don't insert an extra brace in macros with native newlines

Due to `format_snippet` formatting the input with \r\n the subtraction
would wouldn't give a length that removed the }

Fixes #2641

src/lib.rs

@@ -645,7 +645,7 @@ pub fn format_code_block(code_snippet: &str, config: &Config) -> Option<String>
     // then unindent the whole code block.
     let formatted = format_snippet(&snippet, config)?;
     // 2 = "}\n"
-    let block_len = formatted.len().checked_sub(2).unwrap_or(0);
+    let block_len = formatted.rfind('}').unwrap_or(formatted.len());
     let mut is_indented = true;
     for (kind, ref line) in LineClasses::new(&formatted[FN_MAIN_PREFIX.len()..block_len]) {
         if !is_first {

tests/config/issue-2641.toml

@@ -0,0 +1 @@
+newline_style = "Windows"

tests/source/issue-2641.rs

@@ -0,0 +1,3 @@
+macro_rules! a {
+    () => {{}}
+}

tests/target/issue-2641.rs

@@ -0,0 +1,3 @@
+macro_rules! a {
+    () => {{}};
+}