website: Fixed website source URL to stable branch

Author: BobbyRBruce

_config.yml

@@ -1,6 +1,6 @@
 # Site Settings
 title: gem5
-sourceurl: "https://gem5.googlesource.com/public/gem5-website/+/refs/heads/master/README.md"
+sourceurl: "https://gem5.googlesource.com/public/gem5-website/+/refs/heads/stable/README.md"
 url: "https://www.gem5.org/"
 
 defaults:

_config_dev.yml

@@ -1,6 +1,6 @@
 # Site Settings
 title: gem5
-sourceurl: "https://gem5.googlesource.com/public/gem5-website/+/refs/heads/master/README.md"
+sourceurl: "https://gem5.googlesource.com/public/gem5-website/+/refs/heads/stable/README.md"
 url: "http://localhost:4000"
 baseurl: ""
 

_pages/documentation/learning_gem5/part0_introduction.md

@@ -31,7 +31,7 @@ tools like gem5, it is important to actually understand how it works
 before using it.
 
 You can find the source for this book at
-<https://gem5.googlesource.com/public/gem5-website/+/refs/heads/master/_pages/documentation/learning_gem5/>.
+<https://gem5.googlesource.com/public/gem5-website/+/refs/heads/stable/_pages/documentation/learning_gem5/>.
 
 ## What is gem5?
 

_pages/documentation/reporting_problems.md

@@ -77,5 +77,5 @@ on how to do this.
 
 If your issue is with the content of a gem5 document/tutorial being incorrect,
 then please consider submitting a change. Please consult our [README](
-https://gem5.googlesource.com/public/gem5-website/+/refs/heads/master/README.md)
+https://gem5.googlesource.com/public/gem5-website/+/refs/heads/stable/README.md)
 for more information on how to make contributions to the gem5 website.