Revert "Development of 4.1.0 started."

This reverts commit 010dcf8.

Author: k0kubun

include/ruby/version.h

@@ -67,7 +67,7 @@
  * Minor  version.   As of  writing  this  version changes  annually.   Greater
  * version doesn't mean "better"; they just mean years passed.
  */
-#define RUBY_API_VERSION_MINOR 1
+#define RUBY_API_VERSION_MINOR 0
 
 /**
  * Teeny version.  This digit  is kind of reserved these days.   Kept 0 for the