hterm: set sans-serif font for find bar
hterm: set sans-serif font for find bar

Change-Id: I1fa8625cbbc5dc0ee56e0895109e0fc6f9745275
Reviewed-on: https://chromium-review.googlesource.com/c/apps/libapps/+/2330671
Reviewed-by: Shivang Garg <0f0d2bd68e28c3b10856e5f45d2aab3cef33f47a@google.com>
Tested-by: kokoro <2ac7b1f3fa578934c95181d4272be0d3bca00121@google.com>

chromium/hterm,chromium/hterm,chromium/hterm,chromium/hterm