[MM-61077] Fix errcheck issues in server/channels/web/static.go (#29285)

Co-authored-by: Ben Schumacher <ben.schumacher@mattermost.com>

server/.golangci.yml

@@ -190,7 +190,6 @@ issues:
         channels/utils/license_test.go|\
         channels/web/oauth_test.go|\
         channels/web/saml.go|\
-        channels/web/static.go|\
         channels/web/web_test.go|\
         channels/web/webhook.go|\
         cmd/mattermost/commands/cmdtestlib.go|\