.mailmap: add an alias for Eleni Maria Stea

Signed-off-by: Andres Gomez <agomez@igalia.com>
Reviewed-by: Eleni Maria Stea <elene.mst@gmail.com>
Part-of: <!9435>
3 jobs for !9435 with tanty/eleni in 19 seconds (queued for 1 second)
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