Proposing a PR to fix a few small typos

[timgates42]

Issue Type

[x] Bug (Typo)

Steps to Replicate and Expected Behaviour

• Examine pygubu/widgets/calendarframe.py, pygubu/widgets/combobox.py and observe initializating, however expect to see initialization.
• Examine pygubu/stockimage.py and observe suported, however expect to see supported.

Notes

Semi-automated issue generated by
https://github.com/timgates42/meticulous/blob/master/docs/NOTE.md

To avoid wasting CI processing resources a branch with the fix has been
prepared but a pull request has not yet been created. A pull request fixing
the issue can be prepared from the link below, feel free to create it or
request @timgates42 create the PR. Alternatively if the fix is undesired please
close the issue with a small comment about the reasoning.

https://github.com/timgates42/pygubu/pull/new/bugfix_typos

Thanks.