Fix `String.capitalize()` description to follow camelCase changes

This closes #40093.

(cherry picked from commit 887099680a7ae2aca53ef0e944fc408e0d333591)

doc/classes/String.xml

@@ -260,7 +260,7 @@
 			<return type="String">
 			</return>
 			<description>
-				Changes the case of some letters. Replaces underscores with spaces, converts all letters to lowercase, then capitalizes first and every letter following the space character. For [code]capitalize camelCase mixed_with_underscores[/code], it will return [code]Capitalize Camelcase Mixed With Underscores[/code].
+				Changes the case of some letters. Replaces underscores with spaces, adds spaces before in-word uppercase characters, converts all letters to lowercase, then capitalizes the first letter and every letter following a space character. For [code]capitalize camelCase mixed_with_underscores[/code], it will return [code]Capitalize Camel Case Mixed With Underscores[/code].
 			</description>
 		</method>
 		<method name="casecmp_to">