fix: remove enum in declaration
fix: remove enum in declaration

SymmetricTensorEigenvectorMethod is an enum class. MSVC complains about
"a scoped enumeration cannot be redeclared as an unscoped enumeration",
which is a bit weird. I do think this fix is correct, though.

sairajat/dealii,sairajat/dealii,naliboff/dealii,naliboff/dealii,danshapero/dealii,danshapero/dealii,danshapero/dealii,danshapero/dealii,naliboff/dealii,sairajat/dealii,sairajat/dealii,danshapero/dealii,danshapero/dealii,naliboff/dealii,naliboff/dealii,sairajat/dealii,sairajat/dealii,danshapero/dealii,sairajat/dealii,naliboff/dealii,naliboff/dealii