mgm: remove untested gating from tested methods (#623)

Removes the `#[cfg(feature = "untested")]` gating from all methods
tested in `tests/integration.rs` and their dependent codepaths.

src/consts.rs

@@ -1,6 +1,7 @@
-#![allow(dead_code)]
 //! Miscellaneous constant values
 
+#![allow(dead_code)]
+
 /// YubiKey max buffer size
 pub(crate) const CB_BUF_MAX: usize = 3072;
 
@@ -8,7 +9,6 @@ pub(crate) const CB_BUF_MAX: usize = 3072;
 pub(crate) const CB_OBJ_MAX: usize = CB_BUF_MAX - 9;
 
 pub(crate) const CB_OBJ_TAG_MIN: usize = 2; // 1 byte tag + 1 byte len
-#[cfg(feature = "untested")]
 pub(crate) const CB_OBJ_TAG_MAX: usize = CB_OBJ_TAG_MIN + 2; // 1 byte tag + 3 bytes len
 
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