doc: drop scheme from links that are known to support HTTPS

golang.org now serves HTTPS with a valid cert, so it's reasonable
that users should click through to the HTTPS versions of *.golang.org
and other known sites.

LGTM=bradfitz
R=golang-codereviews, bradfitz
CC=golang-codereviews
https://golang.org/cl/112650043
diff --git a/doc/install-source.html b/doc/install-source.html
index 6f6a15a..82859b5 100644
--- a/doc/install-source.html
+++ b/doc/install-source.html
@@ -81,7 +81,7 @@
 
 <p>
 The Go tool chain is written in C. To build it, you need a C compiler installed. 
-Please refer to the <a href="http://code.google.com/p/go-wiki/wiki/InstallFromSource#Install_C_tools">InstallFromSource</a>
+Please refer to the <a href="//golang.org/wiki/InstallFromSource#Install_C_tools">InstallFromSource</a>
 page on the Go community Wiki for operating system specific instructions.
 </p>
 
@@ -283,16 +283,16 @@
 The usual community resources such as
 <code>#go-nuts</code> on the <a href="http://freenode.net/">Freenode</a> IRC server
 and the
-<a href="http://groups.google.com/group/golang-nuts">Go Nuts</a>
+<a href="//groups.google.com/group/golang-nuts">Go Nuts</a>
 mailing list have active developers that can help you with problems
 with your installation or your development work.
 For those who wish to keep up to date,
-there is another mailing list, <a href="http://groups.google.com/group/golang-checkins">golang-checkins</a>,
+there is another mailing list, <a href="//groups.google.com/group/golang-checkins">golang-checkins</a>,
 that receives a message summarizing each checkin to the Go repository.
 </p>
 
 <p>
-Bugs can be reported using the <a href="http://code.google.com/p/go/issues/list">Go issue tracker</a>.
+Bugs can be reported using the <a href="//code.google.com/p/go/issues/list">Go issue tracker</a>.
 </p>
 
 
@@ -306,7 +306,7 @@
 <p>
 The <code>release</code> tag refers to the current stable release of Go.
 Most Go users should use this version. New releases are announced on the
-<a href="http://groups.google.com/group/golang-announce">golang-announce</a>
+<a href="//groups.google.com/group/golang-announce">golang-announce</a>
 mailing list.
 </p>
 
@@ -482,8 +482,8 @@
 <p>
 If in doubt, leave this variable unset, and adjust it if required
 when you first run the Go executable.
-The <a href="http://code.google.com/p/go-wiki/wiki/GoArm">GoARM</a> page
-on the <a href="http://code.google.com/p/go-wiki/w/list">Go community wiki</a>
+The <a href="//golang.org/wiki/GoArm">GoARM</a> page
+on the <a href="//golang.org/wiki">Go community wiki</a>
 contains further details regarding Go's ARM support.
 </p>