fix: pass cmp.Options to cmp.Diff in BeComparableToMatcher

[bartlomiej-grzegorek]

Small fix to this PR introduced @xiantank.
As additional cmp.Options might be passed to cmp.Equal method, the same should be passed to cmp.Diff.
In worst cases, lacking of options might cause a panic; eg. while using

type structWithUnexportedFields struct {
    unexported string
    Exported   string
}

actual := structWithUnexportedFields{unexported: "xxx", Exported: "exported field value"}
expectedEqual := structWithUnexportedFields{unexported: "yyy", Exported: "exported field value"}
Expect(actual).To(BeComparableTo(expectedEqual, cmpopts.IgnoreUnexported(structWithUnexportedFields{}))

If the exported values were different, cmp.Equal returns false and FailureMessage will panic because cmp.Diff can't handle unexported fields.

[onsi]

thanks for this - makes sense. I'll pull it in once the GitHub actions go green.