UNIVERSAL::VERSION should treat "version" as a string

UNIVERSAL::VERSION should treat "version" as a string

It was treating it as a version object and then failing the validation
test, instead of treating it as an invalid version format, as it does
with "versions":

$ ./perl -Ilib -e'$VERSION = "versions"; main->VERSION(1)'
Invalid version format (dotted-decimal versions require at least three parts) at -e line 1.
$ ./perl -Ilib -e'$VERSION = "version"; main->VERSION(1)'
Invalid version object at -e line 1.

See also perl #102586.