Set limit for execution in C# linter
Set limit for execution in C# linter

Summary: This sets the limit for future execution in the C# linter to 8.  See D7606 for more information.

Test Plan:
Ran

```
arc lint --everything --trace --never-apply-patches --output json
```

and saw it only run 8 commands at once.

Reviewers: epriestley, #blessed_reviewers

Reviewed By: epriestley

CC: Korvin, epriestley, aran

Differential Revision: https://secure.phabricator.com/D7607

dguo-coursera/arcanist,r4nt/arcanist,hach-que/arcanist,wikimedia/phabricator-arcanist,wxstars/arcanist,aik099/arcanist,PageUpPeopleOrg/arcanist-patches,memsql/arcanist,alexmv/arcanist,calblueprint/arcanist,hach-que/arcanist,fivestars/arcanist,sneakpeeq/arcanist,phacility/arcanist,dguo-coursera/arcanist,chundongwang/arcanist,codelabs-ch/arcanist,jra3/arcanist,codelabs-ch/arcanist,codelabs-ch/arcanist,folsom-labs/arcanist,uber/arcanist,Symplicity/arcanist,phacility/arcanist,wharris/arcanist,Khan/arcanist,wharris/arcanist,memsql/arcanist,wxstars/arcanist,zhihu/arcanist,memsql/arcanist,aik099/arcanist,coursera/arcanist,eSpark/arcanist,KieranHayes/arcanist,calblueprint/arcanist,kevinseelbach/arcanist,julkiewicz/arcanist,sneakpeeq/arcanist,fivestars/arcanist,sneakpeeq/arcanist,KieranHayes/arcanist,zhihu/arcanist,codelabs-ch/arcanist,uber/arcanist,hach-que/arcanist,chundongwang/arcanist,uber/arcanist,calblueprint/arcanist,phacility/arcanist,fivestars/arcanist,wharris/arcanist,julkiewicz/arcanist,phacility/arcanist,calblueprint/arcanist,Khan/arcanist,wikimedia/phabricator-arcanist,wharris/arcanist,PageUpPeopleOrg/arcanist-patches,julkiewicz/arcanist,haskell-infra/arcanist,dguo-coursera/arcanist,PageUpPeopleOrg/arcanist-patches,fivestars/arcanist,folsom-labs/arcanist,alexmv/arcanist,alexmv/arcanist,Symplicity/arcanist,Symplicity/arcanist,zhihu/arcanist,r4nt/arcanist,zhihu/arcanist,uber/arcanist,aik099/arcanist,haskell-infra/arcanist,sneakpeeq/arcanist,folsom-labs/arcanist,codelabs-ch/arcanist,wxstars/arcanist,jra3/arcanist,coursera/arcanist,r4nt/arcanist,kevinseelbach/arcanist,dguo-coursera/arcanist,wxstars/arcanist,chundongwang/arcanist,phacility/arcanist,wikimedia/phabricator-arcanist,jra3/arcanist,r4nt/arcanist,folsom-labs/arcanist,haskell-infra/arcanist,KieranHayes/arcanist,jra3/arcanist,Symplicity/arcanist,hach-que/arcanist,eSpark/arcanist,coursera/arcanist,wikimedia/phabricator-arcanist,Khan/arcanist,PageUpPeopleOrg/arcanist-patches,Khan/arcanist,julkiewicz/arcanist,memsql/arcanist,kevinseelbach/arcanist,eSpark/arcanist,haskell-infra/arcanist,kevinseelbach/arcanist,coursera/arcanist,chundongwang/arcanist,aik099/arcanist,KieranHayes/arcanist,eSpark/arcanist,alexmv/arcanist