Use requiredVersionToText in logged warning

[pbrisbin]

Before, this warning looked like:

2023-09-28 14:39:53 [error    ] Incompatible Stackctl version
                                current=1.5.0.0
                                required=RequiredVersion {requiredVersionOp = RequiredVersionIsh, requiredVersionCompareWith = Version {versionBranch = [1,4], versionTags = []}}

Now, it looks like:

2023-09-28 14:40:11 [error    ] Incompatible Stackctl version   current=1.5.0.0 required="=~ 1.4"

NOTE: the show may seem redundant now, but it was kept to make the value come out quoted (and escaped, if that's ever necessary).