Fix Typos in LSTMTimeSeriesMultivariate

[pandeynandancse]

Please have a look,

[mlpack-bot[bot]]

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[kartikdutt18]

Thanks for opening this PR. Looks good to me. Also if you are looking for examples we have examples repo with all these files as well as notebooks. Thanks.

[mlpack-bot[bot]]

Hello there! Thanks for your contribution. I see that this is your first contribution to mlpack. If you'd like to add your name to the list of contributors in COPYRIGHT.txt and you haven't already, please feel free to push a change to this PR---or, if it gets merged before you can, feel free to open another PR.

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[pandeynandancse]

Actually @birm has approved the changes but unknowingly I requested again for review. Sorry for any inconvenience. Glad to see if PR is merged.