fix strip use

[ahartikainen]

Some of the strip use was wrong, this PR replace these with regex.

[codecov]

Codecov Report

Merging #1351 into master will decrease coverage by 0.01%.
The diff coverage is 90.00%.

@@            Coverage Diff             @@
##           master    #1351      +/-   ##
==========================================
- Coverage   91.80%   91.78%   -0.02%     
==========================================
  Files         101      101              
  Lines       10636    10642       +6     
==========================================
+ Hits         9764     9768       +4     
- Misses        872      874       +2     

Impacted Files	Coverage Δ
arviz/data/io_cmdstan.py	91.45% <90.00%> (-0.35%)	⬇️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 6411cde...666282f. Read the comment docs.