clear forced xsi:type attribute state in ToXmlGenerator.writeName

[Sahana2524]

writeName's synthetic xsi:type handling forces attribute mode and the XSI namespace onto the next value, and only the bean-serializer path clears it (by assigning the next name through setNextName):

• a Map / JsonNode / @JsonAnyGetter key of xsi:type leaves every following sibling as an xsi:-prefixed attribute instead of an element
• {"xsi:type":"A","type":"B"} emits a duplicate xsi:type attribute, so the module produces XML it can no longer read back
• {"xsi:type":"T","nil":"true"} emits xsi:nil="true", so the whole document reads back as null

Clears the forced state on the next writeName for the content-driven case; the bean path already reset it via setNextName, so legitimate polymorphic output is unchanged.

[github-actions]

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