roachtest: remove now-unnecessary hack

Closes cockroachdb#27717.

Release note: None

pkg/cmd/roachtest/upgrade.go

@@ -48,17 +48,7 @@ func registerUpgrade(r *registry) {
  c.Put(ctx, b, "./cockroach", c.Range(1, nodes))
  // Force disable encryption.
  // TODO(mberhault): allow it once oldVersion >= 2.1.
- start := func() {
- c.Start(ctx, c.Range(1, nodes), startArgsDontEncrypt)
- }
- start()
- time.Sleep(5 * time.Second)
-
- // TODO(tschottdorf): this is a hack similar to the one in the mixed version
- // test. Remove it when we have a 2.0.x binary that has #27639 fixed.
- c.Stop(ctx, c.Range(1, nodes))
- start()
- time.Sleep(5 * time.Second)
+ c.Start(ctx, c.Range(1, nodes), startArgsDontEncrypt)
 
  const stageDuration = 30 * time.Second
  const timeUntilStoreDead = 90 * time.Second
@@ -266,7 +256,7 @@ func registerUpgrade(r *registry) {
  }
  }
 
- const oldVersion = "v2.0.0"
+ const oldVersion = "v2.0.5"
  for _, n := range []int{5} {
  r.Add(testSpec{
  Name: fmt.Sprintf("upgrade/oldVersion=%s/nodes=%d", oldVersion, n),