Rich text: preserve white space should strip \r (#58805)

Co-authored-by: ellatrix <ellatrix@git.wordpress.org>
Co-authored-by: t-hamano <wildworks@git.wordpress.org>

packages/rich-text/src/create.js

@@ -401,14 +401,26 @@ function collapseWhiteSpace( element, isRoot = true ) {
 }
 
 /**
- * Removes reserved characters used by rich-text (zero width non breaking spaces added by `toTree` and object replacement characters).
+ * We need to normalise line breaks to `\n` so they are consistent across
+ * platforms and serialised properly. Not removing \r would cause it to
+ * linger and result in double line breaks when whitespace is preserved.
+ */
+const CARRIAGE_RETURN = '\r';
+
+/**
+ * Removes reserved characters used by rich-text (zero width non breaking spaces
+ * added by `toTree` and object replacement characters).
  *
  * @param {string} string
  */
 export function removeReservedCharacters( string ) {
-	// with the global flag, note that we should create a new regex each time OR reset lastIndex state.
+	// with the global flag, note that we should create a new regex each time OR
+	// reset lastIndex state.
 	return string.replace(
-		new RegExp( `[${ ZWNBSP }${ OBJECT_REPLACEMENT_CHARACTER }]`, 'gu' ),
+		new RegExp(
+			`[${ ZWNBSP }${ OBJECT_REPLACEMENT_CHARACTER }${ CARRIAGE_RETURN }]`,
+			'gu'
+		),
 		''
 	);
 }