Consider creating an option to mimic previous tab behavior

[non-Jedi]

Per @ronisbr, #185 significantly change the behavior of TAB.

https://github.com/JuliaEditorSupport/julia-emacs/issues/188#issuecomment-1542914710:

If I use the latest commit with (setq julia-force-tab-complete t) (default), I can replace LaTeX symbols by pressing TAB. For example, "\alpha<TAB>" gives α. However, in this case, TAB always force indentation update. Hence, I am not able, for example, to increase the indentation by pressing TAB repeatedly as I could before.

If I set (setq julia-force-tab-complete nil), now I can increase the indentation by pressing TAB repeatedly. However, I lost the ability to replace LaTeX symbol by hitting TAB. In this case, I must use C-SPC, which is my default completion keystroke.

I am not saying we must revert to the old behavior. I am just saying that the behavior has changed and I am not certain if this is a bug or how the new system must work.

To me, this brings TAB behavior back in line with how users of the rest of emacs would expect it to behave, and I see it as a benefit. If there's sufficient interest, I could create a configuration option that would cause TAB to simulate the old behavior.