Browser-laptop: Update Muon to 4.5.31

[bsclifton]

Chromium 63.0.3239.108

Test plan

1. Visit about:brave
2. Ensure Muon version matches
3. Ensure libchromiumcontent version is correct

[bsclifton]

Updated to 4.5.22 with 37406b9a2c98d88daac29f2824285db05e2a970a

[srirambv]

0.19.109 on 4.5.23 with 9c674b5

[bsclifton]

Updated to 4.5.25 with c36e597be1debe1326693a6c132480c3471a158b

[kjozwiak]

Clearing the checked tags to make sure that 4.5.25 is now being used.

[bsclifton]

Updated to 4.5.26 with https://github.com/brave/browser-laptop/commit/03410e18d05071c948974175c1482ecb282521b0

[bsclifton]

Updated to 4.5.28 with d3b15a6e96a0b1b4286779de02b9181ae2a63fab

[bsclifton]

Updated to 4.5.30 with https://github.com/brave/browser-laptop/commit/1eb971bcbcb11cb5ba453da087f99d6f6f407206

[luixxiul]

Removing the checked labels to make sure this issue re-checked.

[bsclifton]

Updated to 4.5.31 with https://github.com/brave/browser-laptop/commit/647c86573e9a1a5ff8fd461a6333ac9755e8ee42

Removing labels 😄

[kjozwiak]

Also ensured that 63.0.3239.108 was the correct Chromium build via https://github.com/brave/muon/commit/0a0bcfda36360564e608b9a3e202317ed54333a6