Use Array.prototype.filter(Boolean) more, when filtering out truthy values

[Snuffleupagus]

There are some spots where we want to filter out any truthy values, where that's currently done with an arrow function. Those cases can instead use Boolean as the callback function, which is a pattern that newer parts of the code-base is already using.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 90.16%. Comparing base (b96d745) to head (92b2cd3).
⚠️ Report is 2 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master   #21781   +/-   ##
=======================================
  Coverage   90.15%   90.16%           
=======================================
  Files         264      264           
  Lines       67253    67250    -3     
=======================================
+ Hits        60632    60635    +3     
+ Misses       6621     6615    -6     

Flag	Coverage Δ
browsertest	66.35% <40.00%> (+0.02%)	⬆️
fonttest	9.00% <ø> (ø)
integrationtest	69.38% <60.00%> (+0.01%)	⬆️
unittest	58.26% <100.00%> (-0.01%)	⬇️
unittestcli	56.80% <100.00%> (+<0.01%)	⬆️

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[Snuffleupagus]

/botio browsertest

[moz-tools-bot]

From: Bot.io (Linux m4)

---

Received

Command cmd_browsertest from @Snuffleupagus received. Current queue size: 0

Live output at: http://54.241.84.105:8877/df35ad3abc52c28/output.txt

[moz-tools-bot]

From: Bot.io (Windows)

---

Received

Command cmd_browsertest from @Snuffleupagus received. Current queue size: 0

Live output at: http://54.193.163.58:8877/521ecb2bac9772c/output.txt

[moz-tools-bot]

From: Bot.io (Linux m4)

---

Success

Full output at http://54.241.84.105:8877/df35ad3abc52c28/output.txt

Total script time: 18.20 mins

• Regression tests: Passed

[moz-tools-bot]

From: Bot.io (Windows)

---

Success

Full output at http://54.193.163.58:8877/521ecb2bac9772c/output.txt

Total script time: 23.63 mins

• Regression tests: Passed

[calixteman]

LGTM. Thank you.

[timvandermeij]

Looks better; thanks!