v0.4.9

Trixi v0.4.9

Diff since v0.4.8

Merged pull requests:

• reduce CI times (#972) (@ranocha)
• make some coverage tests in p4est_part2 cheaper (#973) (@ranocha)
• bump StartUpDG.jl version (#974) (@jlchan)
• Enable 1D DGMulti solvers (#975) (@jlchan)