symbols/in: rename a layout, by mentioning the script instead of the font

"Eeyek" is the name of a font [1], not the name of the relevant script. The script is called "Meitei" [2], like the language and the people. The official name of the language is "Manipuri", and its code mni.

[1] https://sources.debian.org/patches/fonts-eeyek/ [2] https://en.wikipedia.org/wiki/Meitei_script

So, rename and re-identify the layout accordingly, and add an alias from eeyek to mni.

(Note: without a specific Eeyek font installed, the Meitei script displays fine here, in browswer, terminal, and editor.)

Also, drop the third-level chooser, as the layout does not contain anything above the two base levels.

Signed-off-by: Benno Schulenberg bensberg@telfort.nl