rename master to main

Author: jhuleatt

quickstarts/test-complete/README.md

@@ -28,4 +28,4 @@ completion of a test matrix in **Firebase Test Lab**.
 ## Next Steps
 
 To see how to post to Slack instead of just `console.log`-ing, check out
-[this sample](https://github.com/firebase/functions-samples/tree/master/testlab-to-slack).
+[this sample](https://github.com/firebase/functions-samples/tree/main/testlab-to-slack).

stripe/public/index.html

@@ -95,7 +95,7 @@ <h2>Payments</h2>
     <hr />
     <footer>
       <a
-        href="https://github.com/firebase/functions-samples/tree/master/stripe"
+        href="https://github.com/firebase/functions-samples/tree/main/stripe"
       >
         View source code
       </a>

user-data-cleanup/doc/auto_rules_extraction.md

@@ -1,2 +1,2 @@
-**Moved to https://github.com/firebase/user-data-protection/blob/master/doc/auto_rules_extraction.md**
+**Moved to https://github.com/firebase/user-data-protection/blob/main/doc/auto_rules_extraction.md**
 

user-data-cleanup/doc/design.md

@@ -1 +1 @@
-**Moved to https://github.com/firebase/user-data-protection/blob/master/doc/design.md**
+**Moved to https://github.com/firebase/user-data-protection/blob/main/doc/design.md**