ruby_2_4: remove

According to https://endoflife.software/programming-languages/server-side-scripting/ruby
ruby 2.4 will go end-of-life in march, where the new release of nixpkgs
will be cut. We won't be able to support it for security updates.

Remove all references to ruby_2_4 and add ruby_2_7 instead where
missing.

Mark packages that depend on ruby 2.4 as broken:
* chefdk
* sonic-pi

pkgs/development/interpreters/ruby/default.nix

@@ -26,7 +26,6 @@ let
   generic = { version, sha256 }: let
     ver = version;
     tag = ver.gitTag;
-    atLeast25 = lib.versionAtLeast ver.majMin "2.5";
     atLeast27 = lib.versionAtLeast ver.majMin "2.7";
     baseruby = self.override {
       useRailsExpress = false;
@@ -77,14 +76,13 @@ let
         nativeBuildInputs = [ autoreconfHook bison ]
           ++ (op docSupport groff)
           ++ op (stdenv.buildPlatform != stdenv.hostPlatform) buildPackages.ruby;
-        buildInputs =
-             (op fiddleSupport libffi)
+        buildInputs = [ autoconf ]
+          ++ (op fiddleSupport libffi)
           ++ (ops cursesSupport [ ncurses readline ])
           ++ (op zlibSupport zlib)
           ++ (op opensslSupport openssl)
           ++ (op gdbmSupport gdbm)
           ++ (op yamlSupport libyaml)
-          ++ (op atLeast25 autoconf)
           # Looks like ruby fails to build on darwin without readline even if curses
           # support is not enabled, so add readline to the build inputs if curses
           # support is disabled (if it's enabled, we already have it) and we're
@@ -106,15 +104,10 @@ let
           cp -r ${rubygems}/test/rubygems $sourceRoot/test
         '';
 
-        postPatch = if atLeast25 then ''
+        postPatch = ''
           sed -i configure.ac -e '/config.guess/d'
           cp --remove-destination ${config}/config.guess tool/
           cp --remove-destination ${config}/config.sub tool/
-        ''
-        else opString useRailsExpress ''
-          sed -i configure.in -e '/config.guess/d'
-          cp ${config}/config.guess tool/
-          cp ${config}/config.sub tool/
         '';
 
         # Force the revision.h generation. Somehow `revision.tmp` is an empty
@@ -230,14 +223,6 @@ let
     ) args; in self;
 
 in {
-  ruby_2_4 = generic {
-    version = rubyVersion "2" "4" "9" "";
-    sha256 = {
-      src = "1bn6n5b920qy3lsx99jr8495jkc3sg89swgb96d5fgd579g6p6zr";
-      git = "066kb1iki7mx7qkm10xhj5b6v8s47wg68v43l3nc36y2hyim1w2c";
-    };
-  };
-
   ruby_2_5 = generic {
     version = rubyVersion "2" "5" "7" "";
     sha256 = {