These edits all relate to commit 71927e1 from PR tc39#1480.

- Markup: repair a malformed <emu-xref> tag

- Editorial: Append "then" to "If" steps

- Markup: change hyphens to dots in clause-id for String.prototype.matchAll

- Editorial: Change RIGHT SINGLE QUOTATION MARK to APOSTROPHE
  (U+2019 to U+0027)

- Markup: Remove underscores from "_CreateRegExpStringIterator_"
  ... because it's not a variable.

- Editorial: dissolve 2 <emu-xref> elements
  ... that should be handled by ecmarkup's auto-linking.

- Markup: Use conventional format for clause-ids
  (for clauses relating to RegExp String Iterator Object + Instances)

- Editorial: Define %RegExpStringIteratorPrototype% like other intrinsics

- Editorial: Insert space before square-bracket
  ... in "%RegExpStringIteratorPrototype% [ @@toStringTag ]"

- Editorial: Hoist "Properties of RegExp String Iterator Instances" clause
  Move it 'up' one level
  (pop it out of "The %RegExpStringIteratorPrototype% Object" clause),
  because it's not defining a property of %RegExpStringIteratorPrototype%.

- Markup: Tweak "Internal Slots of RegExp String Iterator Instances" table.
  Change <figure>/<figurecaption>/<span> to <emu-table>.
  Change the id from "table-1" to something more mnemonic.
  Delete spurious "<tr>" tag.
  Refer to it with an <emu-xref> rather than an <a> element.

(Originally, these were 11 separate commits,
but @ljharb requested that I collapse them.)