Fix "text" ctype in smb_enumshares

"text" is not a valid ctype, should be text/plain.

- [x] Use auxiliary/scanner/smb/smb_enumshares
- [x] Have a valid username/pass
- [x] Set ```SpiderShares``` to true
- [x] Set ```ShowFiles``` to true
- [x] Set ```LogSpider``` between 1, 2 or 3
- [x] Run the module. It should list all the files found, and store the results with a store_loot as *.txt