Clarify source availability in MFA criteria (#2113)

docs/multi-factor-authentication.md

@@ -132,7 +132,7 @@ We highly recommend that you use mobile TOTP apps instead of desktop alternative
 
     We are working on establishing defined criteria for every section of our site, and this may be subject to change. If you have any questions about our criteria, please [ask on our forum](https://discuss.privacyguides.net/latest) and don't assume we didn't consider something when making our recommendations if it is not listed here. There are many factors considered and discussed when we recommend a project, and documenting every single one is a work-in-progress.
 
-- Must be open-source software.
+- Source code must be publicly available.
 - Must not require internet connectivity.
 - Must not sync to a third-party cloud sync/backup service.
     - **Optional** E2EE sync support with OS-native tools is acceptable, e.g. encrypted sync via iCloud.