cam2map USEPROJ mode writes misspelled EquitorialRadius keyword (missing "a")

**ISIS version(s) affected**: 10.0.0

**Description**

`cam2map`'s `USEPROJ` branch builds its own `Mapping` group in C++ and writes the radius keyword as `EquitorialRadius` (missing the "a") instead of `EquatorialRadius`:

```cpp
mappingGroup.addKeyword(PvlKeyword("EquitorialRadius", toString(equatorialRadius, 15)));
```

https://github.com/DOI-USGS/ISIS3/blob/10.0.0/isis/src/base/apps/cam2map/cam2map.cpp#L81

**How to reproduce**

Run any `cam2map ... useproj=yes projstring="..."` invocation and inspect the intermediate `userMap`/`print.prt` output, or add a debug print in `cam2map.cpp` before the "copy defaults from camGrp" loop that follows it.

**Possible Solution**

Fix the spelling to `EquatorialRadius` at cam2map.cpp:81.

Open isis/src/base/apps/cam2map/cam2map.cpp around line 81 and inspect the USEPROJ branch that builds the Mapping group. Run a cam2map invocation with useproj=yes and a projstring, then inspect the intermediate userMap or print.prt output. Done means the generated keyword is spelled EquatorialRadius.

Written by the indexing model from the issue text.