Bug 1892948 - Remove duplicated non262 tests; r=mgaudet

This was unfortunately a somewhat manual process:

```
python3 test262-export.py > exported.txt
cat exported.txt |grep "SAVED" |sed -e "s/SAVED //" | xargs git rm
```

However, some things are marked SAVED by the export script that are not
present in `sm/staging`. To find these, I did this from the root
directory:

```
git log -p -1 |grep "\--- a"|sed -e "s/--- a\/js\/src\/tests\/non262/js\/src\/tests\/test262\/staging\/sm/" > files.txt
cat files.txt | xargs find |grep "found"
```

And then restored the missing files. Running the tests locally uncovered
one other mistakenly removed file.

Rather than making this process better, I think it first makes sense to
try to upstream the files marked as SAVED by the export script that
aren't currently upstream. If that's not possible, we should skip them
from the export script.

Differential Revision: https://phabricator.services.mozilla.com/D234729

Author: dminor