PackageTests/NewUpdate: fix skipping flaky tests

RejectFutureIndexStates and UpdateIndexState are marked "skip", but it's
under withRemoteRepo, which causes flakiness before skip is called.

cabal-testsuite/PackageTests/NewUpdate/RejectFutureIndexStates/cabal.test.hs

 import Test.Cabal.Prelude
 import Data.List (isPrefixOf)
 
-main = cabalTest $ withProjectFile "cabal.project" $ withRemoteRepo "repo" $ do
+main = cabalTest $ do
 
   skip "Flaky test failing in `curl`, see #9530"
 
+  testBody
+
+testBody = withProjectFile "cabal.project" $ withRemoteRepo "repo" $ do
+
   output <- last
           . words
           . head

cabal-testsuite/PackageTests/NewUpdate/UpdateIndexState/update-index-state.test.hs

 import Test.Cabal.Prelude
 
-main = cabalTest $ withRemoteRepo "repo" $ do
+main = cabalTest $ do
 
   skip "Flaky test failing in `curl`, see #9530"
 
+  testBody
+
+testBody = withRemoteRepo "repo" $ do
+
   -- The _first_ update call causes a warning about missing mirrors, the warning
   -- is platform-dependent and it's not part of the test expectations, so we
   -- check the output manually.