Fix typo on trooper page.

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1642183002
NOTRY=true
DOCS_PREVIEW= https://skia.org/?cl=1642183002

Review URL: https://codereview.chromium.org/1642183002
1 file changed