Fix check-type-closure for serverless Java installs
Fix check-type-closure for serverless Java installs

I ran into this while trying to reproduce Closure failures locally for
a different CL. Python's built-in remove method on lists returns None
instead of the modified list, which was causing the resulting value in
exec_command to be incorrect when a Java install without a server JVM
was used.

Change-Id: Ib2629b513c2f6401c51654e68792509796366e61
Reviewed-on: https://chromium-review.googlesource.com/c/devtools/devtools-frontend/+/2150731
Reviewed-by: Leo Lee <dfb9f1d1be46085fef28fd5cd417fc7b05fffc38@microsoft.com>
Reviewed-by: Yang Guo <1cf0af8245a3a17a632a2c73531392b0f9761c76@chromium.org>
Commit-Queue: Tony Ross <d5807c9a1621d46cc76cd6770054768aff0ae774@microsoft.com>

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