Editorial: consistent "*undefined* or *null*" ordering

[gibson042]

Just increasing some uniformity in spec text:

$ grep -Eo '^ *([)]|_[^_]*_): .*[*]undefined[*].*' spec.html | \
  sed -r 's#^[^:]*: *##; s#</.*##; s#,*( or a throw.*)?$##; s#.*containing (either )?##' | \
  grep ' or ' | \
  sort | uniq -c | sort -nr
  14 a Property Descriptor or *undefined*
   7 an Object or *undefined*
   7 an Environment Record or *undefined*
   3 a Boolean or *undefined*
   2 a String or *undefined*
   1 an ECMAScript language value, but not *undefined* or *null*
   1 a possibly empty List, each of whose elements is a String or *undefined*
   1 a function object or *undefined*
   1 a Realm Record or *undefined*
   1 a Number, a BigInt, or *undefined*
   1 a Number or *undefined*
   1 a List of either Strings or *undefined*
   1 a List of either Match Records or *undefined*
   1 a BigInt or *undefined*
   1 *undefined* or a String

 grep -Eo '[*](null|undefined)[*] or [*](null|undefined)[*]' spec.html | sort | uniq -c
   3 *null* or *undefined*
  25 *undefined* or *null*

I actually prefer the reading of "null or undefined" (undefined last), but past commits have implicitly chosen the opposite.

[ljharb]

in this case, i think "null and undefined" makes much more sense, since explaining the term "nullish" should start with "null"

[michaelficarra]

WFM