[activesupport] Update links to use https instead of http [ci skip]

[yhirano55]

Summary

• Update links to use https instead of http in activesupport.
• All changes are only in comment blocks. So I've skipped CI.

[rails-bot]

r? @kaspth

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[kamipo]

www. is unneeded.

% curl -v -I https://www.unicode.org/reports/tr15
*   Trying 216.97.88.9...
* Connected to www.unicode.org (216.97.88.9) port 443 (#0)
* TLS 1.2 connection using TLS_DHE_RSA_WITH_AES_256_GCM_SHA384
* Server certificate: unicode.org
* Server certificate: COMODO RSA Organization Validation Secure Server CA
* Server certificate: COMODO RSA Certification Authority
* Server certificate: AddTrust External CA Root
> HEAD /reports/tr15 HTTP/1.1
> Host: www.unicode.org
> User-Agent: curl/7.43.0
> Accept: */*
> 
< HTTP/1.1 301 Moved Permanently
HTTP/1.1 301 Moved Permanently
< Date: Tue, 22 Aug 2017 02:07:00 GMT
Date: Tue, 22 Aug 2017 02:07:00 GMT
< Server: Apache
Server: Apache
< Location: https://unicode.org/reports/tr15/
Location: https://unicode.org/reports/tr15/
< Vary: Accept-Encoding
Vary: Accept-Encoding
< Content-Type: text/html; charset=iso-8859-1
Content-Type: text/html; charset=iso-8859-1

< 
* Connection #0 to host www.unicode.org left intact

[kamipo]

Did you confirmed the page? https://www.unicode.org/reports/tr15/
Looks like that the original link is the right page.

[yhirano55]

@kamipo Thanks for you comments. I'll check all links again, and fix it soon.

[yhirano55]

@kamipo I've checked all links and fixed them.

• Add trailing slash to https://www.limited-entropy.com/padding-oracle-attacks/
• Remove trailing slash from https://memcached.org
• https://www.ietf.org/rfc/rfc4122.txt doesn't have any problems.
• It seems that contents of www.unicode.org is different from between http and https. So I've restored them.