version: Replace references to 8.2

[wenzeslaus]

• [x] Links to latest (current) stable in notebooks use the grass-stable URL.
• [x] singularity: Use tag instead of branch. Use an old tag for the example. Avoid using version in the image name.

8.2 used in examples (no change needed?):

• [x] lib/init/grass.html

Fix based on updates to 8.3 branch (same text or same style):

• [x] general/g.version/g.version.html (example of an output; change needed?)
• [x] rpm/grass.spec (copy the updated file? what is the procedure for syncs or updates?) #2977
• [x] doc/howto_release.md (code for copy-pasting; prepare for 8.4?) #2980
• [x] doc/development/submitting/general.md (instructions for contributors; generalize to avoid need for updates?) #2978

[landam]

@wenzeslaus Still relevant?

[wenzeslaus]

Yes, this is still relevant. There are two questions in the description which I don't know an answer to.

In lib/init/grass.html, version number is in example of possible values --config. Other values are old dates (2020) or hashes and that seems to be just fine. What to do with version number for GRASS GIS?

For general/g.version/g.version.html, the version is in several examples of output from g.version. The context is similar - other versions, dates, and hashes. How to modify this if at all?

Do want to keep updating these with every version? Elsewhere, we were able to reduce these updates (see this PR for examples) and thus reduce the work needed for every release.

[wenzeslaus]

Given the lack of ideas and suggestions here, I just updated the numbers from 8.2 to 8.4. I was trying to avoid these changes elsewhere because these need to be updated with each release. I fixed some dates, years and dropped the dev suffix.

This is now ready for review and inclusion into 8.4.