Reference "main" branches instead of "master" branches.

Both WebRTC and Chromium have migrated from the "master" to the "main" branch.

TBR=hta@webrtc.org

Bug: None
Change-Id: I2b5e6973bdd8fdc9c1bd96e2747a8a9ac2630b14
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/226080
Commit-Queue: Fanny Linderborg <linderborg@webrtc.org>
Reviewed-by: Mirko Bonadei <mbonadei@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#34475}
diff --git a/CODE_OF_CONDUCT.md b/CODE_OF_CONDUCT.md
index 7b48e69..f6b7d0f 100644
--- a/CODE_OF_CONDUCT.md
+++ b/CODE_OF_CONDUCT.md
@@ -61,8 +61,8 @@
 ## Acknowledgements
 
 This Code of Conduct is based on Contributor Covenant, version 1.4,
-available [here](http://contributor-covenant.org/version/1/4) and [Chromium](https://chromium.googlesource.com/chromium/src/+/master/CODE_OF_CONDUCT.md)
+available [here](http://contributor-covenant.org/version/1/4) and [Chromium](https://chromium.googlesource.com/chromium/src/+/main/CODE_OF_CONDUCT.md)
 
 ## License
 
-This Code of Conduct is available for reuse under the Creative Commons Zero (CC0) license.
\ No newline at end of file
+This Code of Conduct is available for reuse under the Creative Commons Zero (CC0) license.