package/ruby: security bump to version 2.7.4

Fixes the following security issues:

- CVE-2021-31810: Trusting FTP PASV responses vulnerability in Net::FTP
- CVE-2021-32066: A StartTLS stripping vulnerability in Net::IMAP
- CVE-2021-31799: A command injection vulnerability in RDoc

For more details, see the announcement:
https://www.ruby-lang.org/en/news/2021/07/07/ruby-2-7-4-released/

Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/ruby/ruby.hash

@@ -1,5 +1,5 @@
-# https://www.ruby-lang.org/en/news/2021/04/05/ruby-2-7-3-released/
-sha256  5e91d1650857d43cd6852e05ac54683351e9c301811ee0bef43a67c4605e7db1  ruby-2.7.3.tar.xz
+# https://www.ruby-lang.org/en/news/2021/07/07/ruby-2-7-4-released/
+sha256  2a80824e0ad6100826b69b9890bf55cfc4cf2b61a1e1330fccbcb30c46cef8d7  ruby-2.7.4.tar.xz
 # License files, Locally calculated
 sha256  b09ca195d2de08f0aacfa8793d0af62d7681c304b3ef714b75813721823295a6  LEGAL
 sha256  967586d538a28955ec2541910cf63c5ac345fcdea94bfb1f1705a1f6eb36bcbb  COPYING

package/ruby/ruby.mk

@@ -5,7 +5,7 @@
 ################################################################################
 
 RUBY_VERSION_MAJOR = 2.7
-RUBY_VERSION = $(RUBY_VERSION_MAJOR).3
+RUBY_VERSION = $(RUBY_VERSION_MAJOR).4
 RUBY_VERSION_EXT = 2.7.0
 RUBY_SITE = http://cache.ruby-lang.org/pub/ruby/$(RUBY_VERSION_MAJOR)
 RUBY_SOURCE = ruby-$(RUBY_VERSION).tar.xz