Remove the implNote in the DOM package description added by JDK-8249643

Through JDK-8249643, an implNote was added to the DOM's package description to document the JDK implementation's deviation from the DOM specification. However, a further study showed that was incorrect because the XML specification did include range [#x10000-#x10FFFF]. The Impl's interpretation was based on "excluding the surrogate blocks". The problem was it used Java char to determine it. Thus instead of excluding the surrogate blocks with codepoints ranging from U+D800 to U+DBFF and U+DC00 to U+DFFF, it converted characters with a Java representation of a surrogate pair into character references.

The implNote added in JDK-8249643 needs to be reverted.