Auto merge of #1892 - EdOverflow:3072-bit-key, r=segiddins

s/2048/3072

# Description:

The default key is size is 3072 and not 2048 bits: beee528

______________

I will abide by the [code of conduct](https://github.com/rubygems/rubygems/blob/master/CODE_OF_CONDUCT.md).

(cherry picked from commit f0c41e7)

Author: homu

lib/rubygems/security.rb

@@ -455,7 +455,7 @@ def self.create_cert_self_signed subject, key, age = ONE_YEAR,
 
   ##
   # Creates a new key pair of the specified +length+ and +algorithm+.  The
-  # default is a 2048 bit RSA key.
+  # default is a 3072 bit RSA key.
 
   def self.create_key length = KEY_LENGTH, algorithm = KEY_ALGORITHM
     algorithm.new length