Update web.config.txt

[brianteeman]

This adds a missing location tag and fixes #6392

I tested the syntax and validity of the web.config.txt using https://webconfigtransformationtester.apphb.com/

[padhie]

Test confirmed - location tag is addeted

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_{This comment was created with the J!Tracker Application at issues.joomla.org/joomla-cms/6398.}

[tecpromotion]

Test confirmed - location tag is closing at the end.

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_{This comment was created with the J!Tracker Application at issues.joomla.org/joomla-cms/6398.}

[knoby2015]

/location tag is in

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_{This comment was created with the J!Tracker Application at issues.joomla.org/joomla-cms/6398.}

[continga]

Test confirmed - location closing tag is added

[Bakual]

Thanks all!

[Yorgoz]

closed