Disable prefer-template.
Disable prefer-template.

The intention is good, but the rule is a bit too strict for us.  In
particular, it complains when using `+` to concatenate multiple lines
for a javascript string.

Auditors: jlfwong

Test plan:
Ran 'ka-lint' in webapp without error.

Khan/khan-linter,Khan/khan-linter,Khan/khan-linter,Khan/khan-linter