[SIEM] [Detection Engine] Import rules upload keeps last file.

[dhurley14]

Kibana version:

Elasticsearch version:

Server OS version:

Browser version:

Browser OS version:

Original install method (e.g. download page, yum, from source, etc.):

Describe the bug:
Importing rules to the detection engine, cancelling, then importing again but with no files selected uses the last file to import.
Steps to reproduce:

1. Click on import
2. select file
3. cancel
4. click on import again
5. click on submit
6. results in rules being uploaded even though a file was not selected on second import.

Expected behavior:

Screenshots (if relevant):

Errors in browser console (if relevant):

Provide logs and/or server output (if relevant):

Any additional context:

[elasticmachine]

Pinging @elastic/siem (Team:SIEM)

[XavierM]

it will be fixed in this PR #56389

[dhurley14]

#56440 (comment)