Increase minimum supported Julia version to v1.10

[sloede]

In Trixi.jl, we are moving to make Julia v1.10 the minimum supported Julia version (trixi-framework/Trixi.jl#2214). For consistency, since v1.10 is an LTS, and since with v1.11 being released, v1.9 is no longer officially supported, I recommend moving to v1.10 as the minimum version for TrixiPartices.jl as well.

Instead of testing on 1.9, recommend instead running tests on v1.11

[efaulhaber]

We are currently running tests on 1.9, 1.10 and 1.11. But if 1.9 is no longer officially supported, we can of course make our lives easier.

[efaulhaber]

Tests in #529 are failing in Julia 1.9. This gives us a good reason to drop support for 1.9 instead of wasting time fixing tests for this old version. @LasNikas

[svchb]

I am fine with removing 1.9.