[stdlib] Fix errant tests

- A benchmark method was renamed during the Set API batch revisions
- The SourceKit test that includes stdlib docs needed a new fixture

benchmark/single-source/SetTests.swift

@@ -13,7 +13,7 @@
 import TestsUtils
 
 @inline(never)
-public func run_SetIsSubset(of N: Int) {
+public func run_SetIsSubsetOf(_ N: Int) {
   let size = 200
 
   SRand()