Remove splitmix SRP (upstream is fixed)

Author: hamishmack

test/cabal.project.local

@@ -1,10 +1,3 @@
--- See https://github.com/haskellari/splitmix/pull/97
-source-repository-package
-  type: git
-  location: https://github.com/hamishmack/splitmix.git
-  tag: e3549473b124a7ba078408ac0d2c8aa8111c3888
-  --sha256: sha256-o18DEF4+z3/jGhMZbow8PFtYBiIm6+b4B+6o5tM6ez0=
-
 if impl(ghc>=9.12.1)
   -- allow newer packages, that are bound to be newer due to
   -- being shipped with a newer compiler.  If you extend this