Remove digest-io from the root workspace (#1330)

This removes the circular dependency chain from the root workspace.

Author: newpavlov

.gitignore

@@ -1,3 +1,2 @@
 target
-**/Cargo.lock
 **/*proptest-regressions

Cargo.lock

@@ -9,15 +9,19 @@ members = [
     "ctutils",
     "cpufeatures",
     "dbl",
-    "digest-io",
     "hex-literal",
     "inout",
     "opaque-debug",
     "wycheproof2blb",
     "zeroize",
-    "zeroize_derive"
+    "zeroize_derive",
+]
+exclude = [
+    # Works only on AArch64
+    "aarch64-dit",
+    # Results in circular dependencies
+    "digest-io",
 ]
-exclude = ["aarch64-dit"]
 
 [profile.dev]
 opt-level = 2