Remove stray comma from info string

There was a stray comma on this info string.  Let's remove it.

Author: traviscross

src/inline-assembly.md

@@ -276,7 +276,7 @@ r[asm.attributes]
 r[asm.attributes.supported-attributes]
 Only the [`cfg`] and [`cfg_attr`] attributes are accepted semantically on inline assembly template strings and operands. Other attributes are parsed, but rejected when the assembly macro is expanded.
 
-```rust,
+```rust
 # fn main() {}
 # #[cfg(target_arch = "x86_64")]
 core::arch::global_asm!(