Fixed issue with Arabic where only a single expansion character was being removed during stemming

[brendon1982]

• [x] Describe in detail what you did and why you did it
  • What you did: I fixed issue with Arabic where only a single expansion character was being removed during stemming. All expansion characters are now removed.
  • Why you did it: The expansion character is only for aesthetic purposes and does not change the meaning of the word. There is no limit to the number of expansion characters a word can have, so when only one is removed instead of all of them, you end up with many versions of the same word in the inverted index, each with a different amount of expansions.
• [x] Add tests. The more the better
  • [x] with at least 1 scenario in case of a bug-fix and 4 scenarios in case of a new language
• [x] Don't open a Pull request for more unrelated topics. (eg a bug-fix, a new language, and few changes to stemming for existing languages in a single pull request)

[MihaiValentin]

Thanks for the contribution @brendon1982 !