bug#34288: Mention how to trigger ':' without filemane

[積丹尼 Dan Jacobson]

OK closing, because I don't exactly remember my main point either.

>>>>> "PE" == Paul Eggert <egg...@cs.ucla.edu> writes:
PE> On 1/31/19 3:42 PM, 積丹尼 Dan Jacobson wrote:
PE> Unfortunately I don't understand this bug report. I don't know what
PE> the "it" is that people would want to figure out.