Fix SAS7BDAT run-length encoding formula
Run across an error/simplification? of a RLE formula in the SAS7BDAT parser. The original code https://bitbucket.org/jaredhobbs/sas7bdat/src/18cbd14407918c1aa90f136c1d6c5d83f307dba0/sas7bdat.py#lines-110:114 has the correct formula. I am not sure why we have another version.

Unfortunately I do not know how to add a regression test. The SAS file that reproduces the issue is proprietary, as is the SAS7BDAT file format, and I'm not aware of any means of creating a SAS file.

- [ ] closes #xxxx (Replace xxxx with the Github issue number)
- [ ] [Tests added and passed](https://pandas.pydata.org/pandas-docs/dev/development/contributing_codebase.html#writing-tests) if fixing a bug or adding a new feature
- [ ] All [code checks passed](https://pandas.pydata.org/pandas-docs/dev/development/contributing_codebase.html#pre-commit).
- [x] Added an entry in the latest `doc/source/whatsnew/vX.X.X.rst` file if fixing a bug or adding a new feature.

Similar case here https://github.com/pandas-dev/pandas/issues/31243#issuecomment-686386759 pyreadstat has the same logic https://github.com/Roche/pyreadstat/blob/master/src/sas/readstat_sas_rle.c#L62-L63 See my note above about a test case. Can add a what’s new  Unfortunately all (shareable) test files I've seen so far, including the ones in pyreadstat, don't  reproduce the bug. A user provided an example SAS file in #44216. Could be helpful, if this SAS file triggers the error you fixed. Unfortunately both of the files do not reproduce the bug cc @bashtage WDYT? Would be good to have a file that requires this offset Is it possible to create one? @bashtage Unfortunately I don't have a file that I can share and pyreadstat can't write SAS7BDAT files. Do you have any ideas where to get such a file? @bashtage came up with a test file by zeroing almost all of the bytes of a real world file. PR now depends on https://github.com/pandas-dev/pandas/pull/47154 > @bashtage came up with a test file by zeroing almost all of the bytes of a real world file. PR now depends on #47154

Once that is in rebase and then should be good.  LGTM. Hello @jonashaag! Thanks for updating this PR. We checked the lines you've touched for [PEP 8](https://www.python.org/dev/peps/pep-0008) issues, and found:



There are currently no PEP 8 issues detected in this Pull Request. Cheers! :beers: 

##### Comment last updated at 2022-07-02 16:18:30 UTC @jreback @mroeschke mind reviewing this? Thanks @jonashaag  Thanks :)