Fix events page inconsistency.

[kosayoda]

I noticed there are a couple spots that still infer that we have 2 jams a year, so feel free to fix those in this PR if you wish, otherwise we can update that content later.

Originally posted by @minalike in #724 (review)

[minalike]

The two spots I noticed:

• "one during the summer and sometimes one during the winter" (I believe this isn't the case anymore, we're pretty squarely in 1 a year territory I believe)
  https://www.pythondiscord.com/events/

• "Our Code Jams happen twice a year. We have a Winter Jam and a Summer Jam."
  https://www.pythondiscord.com/events/code-jams/#how-often-do-these-happen

I found the code jam page itself difficult to find (an easy to miss link on the events page): https://www.pythondiscord.com/events/code-jams/

Maybe we can link it in an "Relevant Links" link block on the side bar of the events page.

• Minor typo: TUIS > TUIs