Executes `svn up` when too old

[TinoDidriksen]

https://github.com/giellalt/template-lang-und/blob/main/m4/giella-macros.m4#L108 actually executes svn up in the current language folder, rather than printing "svn up".

This will be superfluous when svn is deprecated, but now I wonder if other places have backticks that inadvertently execute stuff when printing.

[snomos]

Thanks for reporting. I will check whether there are other places to fix. Help to self:

https://stackoverflow.com/questions/61087875/how-to-escape-backticks-in-bash (but should probably just replace the backticks with regular quotes).