Fix spack build issue when using ^ in depends_on

[simlapointe]

Split depends_on commands to remove ^ usage.

This fixes errors such as:

==> Added repo with namespace 'local'.
==> Error: cannot load package 'palace' from the 'local' repository: the '^' sigil cannot be used in 'depends_on' directives. Please reformulate the directive below as multiple directives:

	depends_on("slepc+cuda cuda_arch=10 ^petsc+cuda cuda_arch=10", when="+cuda+slepc cuda_arch=10")

Error: Process completed with exit code 1.