Update src/items/external-blocks.md

Co-Authored-By: Mazdak Farrokhzad <[email protected]>

Author: gnzlbg

src/items/external-blocks.md

@@ -90,7 +90,7 @@ There are also some platform-specific ABI strings:
 * `extern "vectorcall"` -- The `vectorcall` ABI -- corresponds to MSVC's
   `__vectorcall` and clang's `__attribute__((vectorcall))`
 
-Finally, there are some unstable rustc-specific ABI strings:
+Finally, there are some unstable `rustc`-specific ABI strings:
 
 * `extern "rust-intrinsic"` -- The ABI of rustc intrinsics, equivalent to `"Rust"`.
 * `extern "rust-call"` -- The ABI of the Fn::call trait functions, equivalent to `"Rust"`.