fix: use values that are representable as double in test

Values like 0.1 are not representable as a double which can result in problems, for example:

[...]/dune/common/test/hybridutilitiestest.cc:114:43: error: static assertion failed: Wrong compile time sum!
  114 |   static_assert(sum(numberTupleConstexpr) == 5.1, "Wrong compile time sum!");
      |                 ~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~
[...]/dune/common/test/hybridutilitiestest.cc:114:43: note: the comparison reduces to ‘(5.09999999999999964473e+0l == 5.09999999999999999991e+0l)’

with gcc 13.2.0 on i386.

assigned to @ansgar

mentioned in commit 825f70ca

merged

picked the changes into the branch cherry-pick-825f70ca with commit 2663e9ee

mentioned in commit 2663e9ee

mentioned in merge request !1328 (merged)