build.rs: Drop InCode variant

This has been causing warnings all over the place, just because it was a
marker variant that was currently not in use. As no markers will be
added any more as per the deprecation note, this can go already.

build.rs

@@ -642,8 +642,6 @@ fn main() {
         /// This is equivalent to not having the marker in the first place, except that their
         /// presence serves as a reminder to not reuse that marker name.
         Never,
-        /// A marker that is set if the given string is found in the bindgen output.
-        InCode(&'static str),
         /// A marker that is set if its name is found in the bindgen output. Shorthand for
         /// Text(name).
         NameInCode,
@@ -673,7 +671,6 @@ fn main() {
     ];
     for (needle, name) in markers {
         let found = match needle {
-            InCode(s) => bindgen_output.contains(s),
             NameInCode => bindgen_output.contains(name),
             Always => true,
             Never => false,