SVGHMI: move declaration of "xmlns" javascript const so that widgets can use it.

This was broken in earlier commit, when changing initial execution order because of implementing websocket reconnect.

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                  <xsd:element name="Win32">

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                    <xsd:complexType>

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                      %(toolchain_gcc)s

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                    </xsd:complexType>

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                  </xsd:element>

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