[BUG] mfa g2p considers hidden files and other non-corpus files

[lars76]

Debugging checklist

[x] Have you read the troubleshooting page (https://montreal-forced-aligner.readthedocs.io/en/latest/user_guide/troubleshooting.html) and searched the documentation to ensure that your issue is not addressed there? [x] Have you updated to latest MFA version (check https://montreal-forced-aligner.readthedocs.io/en/latest/changelog/changelog_3.0.html)? What is the output of mfa version? [x] Have you tried rerunning the command with the --clean flag?

Describe the issue mfa g2p considers hidden files (.ipynb_checkpoints/). The statistics shows then an additional speaker (Found X speakers ...) Also, README files are considered as additional data.

For Reproducing your issue Please fill out the following:

1. Corpus structure
   • What language is the corpus in? AISHELL-3
   • How many files/speakers? 218
   • Are you using lab files or TextGrid files for input? lab

Desktop (please complete the following information):

• OS: Linux
• Version ArchLinux
• Any other details about the setup (Cloud, Docker, etc): MFA 3.1