Change mismatch panic message to avoid github linkifying

Author: dtolnay

src/wrapper.rs

@@ -41,11 +41,11 @@ fn mismatch(line: u32) -> ! {
     #[cfg(procmacro2_backtrace)]
     {
         let backtrace = std::backtrace::Backtrace::force_capture();
-        panic!("compiler/fallback mismatch #{}\n\n{}", line, backtrace)
+        panic!("compiler/fallback mismatch L{}\n\n{}", line, backtrace)
     }
     #[cfg(not(procmacro2_backtrace))]
     {
-        panic!("compiler/fallback mismatch #{}", line)
+        panic!("compiler/fallback mismatch L{}", line)
     }
 }