`timeRequired` examples show invalid values.

[christianhujer]

The timeRequired example given 'P30M' probably shall mean "30 minutes". However, 'P30M' actually means a duration of 30 months, which I do not think was the intention. The correct way to specify a duration of 30 minutes is 'PT30M'.

The timeRequired example given 'P1H25M' is invalid, as "P1H25M" is not a valid duration string. The correct way to specify a duration of 1 hour and 25 minutes is 'PT1H25M'.

The timeRequired property: http://schema.org/timeRequired
Description of ISO8601 durations: https://en.wikipedia.org/wiki/ISO_8601#Durations

[philbarker]

@danbri I think this reopening too? I screwed up putting a fix for this issue into an unrelated branch, then reverted the fix, but the PR closed this issue because of the original commit.
PR #1975 closes this issue properly.