Bug 1576083 [wpt PR 18630] - Add missing comma in earlyoom argument l…

…ist, a=testonly

Automatic update from web-platform-tests
Add missing comma in earlyoom argument list (#18630)

Without the comma, the string literals are concatenated.

Spotted via `sudo earlyoom -p -r 60--prefer=(chrome|firefox) --avoid=python`
with a missing space in Taskcluster logs.

This was introduced in web-platform-tests/wpt#15724.
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wpt-commits: b3b48132272f9a92414ce879bd8a5ab468879b8f
wpt-pr: 18630

UltraBlame original commit: 3842950c1e45d64e4ba8c131a589d209e1619dad