update timing format for syllabus

[zkamvar]

This updates the timestamp in the syllabus to read XXh YYm intead of XX:YY
to clearly indicate the units of time.

This will fix #361, which will address carpentries/conversations#40

To preview this change, you can use the {remotes} package:

# install.packages("remotes")
remotes::install_github("carpentries/sandpaper#363")

When you are done, you can re-install the current version of sandpaper like so:

install.packages("sandpaper", repos = "https://carpentries.r-universe.dev")

[tobyhodges]

I like the change to show timing in hours and minutes. However, in reviewing the PR I noticed that the landing page now has the title "Summary and Schedule" in both the Learner and Instructor View. The schedule table only appears in the instructor view, though.

As I guess this is a separate issue, not something introduced in this PR, I am happy to approve.

[zkamvar]

Thank you for the catch, Toby! I've opened a new issue for the bug.