Update submit.rst

Actually Rendered as ``button`` ``submit`` tag (not ``input`` ``submit``)
removed one space

removed one space
minor #4038 Update rendered tag (kirill-oficerov)

This PR was submitted for the 2.5 branch but it was merged into the 2.3 branch instead (closes #4038).

Discussion
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Update rendered tag

Actually Rendered as ``button`` ``submit`` tag (not ``input`` ``submit``)

Commits
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1d50ce5 removed one space
067a447 Update submit.rst