Fix text alignment for MultilineTextInput on Android

[t-arn]

This PR fixes the issue #1807 by removing following code in the set_alignment method of the Android implementation:

        # Refuse to set alignment unless widget has been added to a container.
        # This is because Android EditText requires LayoutParams before
        # setGravity() can be called.
        if not self.native.getLayoutParams():
            return

Although the remark claims that this save guard is needed, I cannot find any problem when removing it.

PR Checklist:

• All new features have been tested
• All new features have been documented
• I have read the CONTRIBUTING.md file
• I will abide by the code of conduct

[t-arn]

@mhsmith Please review this PR

[mhsmith]

Thanks, I'll have a look at this. The code in question was actually added by you in #1591. Did you notice any need for it at that time, or were you only copying it from textinput.py?

The code in textinput.py was added by @paulproteus in #1005, but a lot has changed since then.

[t-arn]

Yes, I also saw that I am to blame for this code. I actually did copy it from textinput. In my own dev branch I fixed it long ago and I never had problems since.

[freakboy3742]

Definitely seems to work in my testing too; I think there's been a few tweaks to the way layouts happen that have made this particular piece of protection code unnecessary.

[mhsmith]

#1938 removes this code from the set_alignment methods of all other widgets. However, similar code still remains in the rehint methods, which may be unnecessary.