Update and fix SDK support table

[helin24]

I forgot to update this table for some previous changes to the min SDK supported setting, and the first row was inaccurate because I probably forgot to account for #7883 back when I first made the table.

Here's the timeline if anyone needs to recreate the logic for updating the table (it was more arduous than I expected):

Release 85.3.2: May 12 2025
- min SDK supported was 3.10.0 (Jan 8 2025)

Release 86.0.1/2: June 13 2025
- min SDK supported was 3.10.3 (from May 29)

Release 87.0: August 5 2025
- min SDK supported was 3.13 (from June 24)

Release 87.1: August 11 2025
- unchanged

Release 88.0.0: October 5 2025
- unchanged

Release 88.1.0: November 13 2025
- unchanged

Release 89.0.0: upcoming
- min SDK supported was 3.16 (from Dec 8)

[helin24]

CC @DanTup. I'm late in updating this, hopefully you've been keeping track better than us.

[DanTup]

CC @DanTup. I'm late in updating this, hopefully you've been keeping track better than us.

I'm slightly behind in dropping Dart 3.1 support, but I had a note to review that this month. Probably I will include the warning that 3.1 is being dropped in the upcoming release, and then actually drop it in 1-2 releases after, making 3.2 the new minimum (which I believe aligns with your Flutter 3.16 - I use the Dart SDK as the trigger).