Update added backticks around a function call

Co-Authored-By: Mazdak Farrokhzad <twingoow@gmail.com>

src/libstd/ffi/c_str.rs

@@ -937,7 +937,7 @@ impl CStr {
     /// This function will wrap the provided `ptr` with a `CStr` wrapper, which
     /// allows inspection and interoperation of non-owned C strings. The total
     /// size of the raw C string must be smaller than `isize::MAX` **bytes**
-    /// in memory due to calling the slice::from_raw_parts function.
+    /// in memory due to calling the `slice::from_raw_parts` function.
     /// This method is unsafe for a number of reasons:
     ///
     /// * There is no guarantee to the validity of `ptr`.