Remove superfluous lines from DSL generated code.

The comma-warning issue has since been fixed, and we don't need to
use `(void) var;` when we have C++17's [[maybe_unused]] attribute.

Change-Id: I2078354f06801b024638e9c7d9ac699df20a8c48
Bug: skia:11854
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/401116
Auto-Submit: John Stiles <johnstiles@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>
11 files changed