better glyph for U+00B0 (DEGREE SIGN)

[Werner LEMBERG]

[texinfo.tex 2022-11-07.17]


I suggest to change the mapping for U+00B0 (DEGREE SIGN) to use
`@textdegree{}`.

```
\input texinfo

@code{45°}

@code{45@textdegree{}}

@bye
```

As this small example document shows, the results look better even
with typewriter IMHO.  Of course, the glyph width must be adjusted for
typewriter, which I haven't done here.


    Werner