Revert "Fix broken CI. (ruby#12963)"

This reverts commit eb91c66.

Author: hsbt

bootstraptest/test_fork.rb

@@ -84,7 +84,7 @@ def now = Process.clock_gettime(Process::CLOCK_MONOTONIC)
 
   10.times do
     pid = fork{ exit!(0) }
-    deadline = now + 30
+    deadline = now + 10
     until Process.waitpid(pid, Process::WNOHANG)
       if now > deadline
         Process.kill(:KILL, pid)

spec/bundler/install/gemfile/git_spec.rb

@@ -1204,7 +1204,7 @@
         gem "foo", :git => "#{lib_path("foo-1.0")}", :branch => "deadbeef"
       G
 
-      expect(err).to match(/deadbeef (not found in upstream origin|does not exist in the repository)/)
+      expect(err).to include("Revision deadbeef does not exist in the repository")
     end
   end