[Usability] The buttons "Master password" and "show passords" should be removed from security tab of preferences dialog

[Zhao Fan]

Bug detailed description:
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The buttons "Master password" and "show passords" should be removed from security tab of preferences dialog.
This is a security problem. If a user doesn't enter a master password and allows the browser to save login and password for any page (like a Bank account login page), the login and password are stored in plain text. Any user can then discover the passwords of the user if they get a hold of the device.

Reproduce steps:
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Launch midbrowser and check the security tab of preferences dialog

Current result:
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There are "Master password" and "show passords" buttons

Expected result:
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The buttons should be removed for security issue

Basic root-causing log:
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[Zhao Fan (fan-zhao)]

Verified with 12/10 image