cleanup_spec: inline path creation.

Let's see if this makes the test more reliable.

Library/Homebrew/test/cleanup_spec.rb

@@ -199,11 +199,8 @@ describe Homebrew::Cleanup do
   describe "::cleanup_logs" do
     let(:path) { (HOMEBREW_LOGS/"delete_me") }
 
-    before do
-      path.mkpath
-    end
-
     it "cleans all logs if prune is 0" do
+      path.mkpath
       described_class.new(days: 0).cleanup_logs
       expect(path).not_to exist
     end
@@ -211,6 +208,7 @@ describe Homebrew::Cleanup do
     it "cleans up logs if older than 30 days" do
       allow_any_instance_of(Pathname).to receive(:ctime).and_return(31.days.ago)
       allow_any_instance_of(Pathname).to receive(:mtime).and_return(31.days.ago)
+      path.mkpath
       subject.cleanup_logs
       expect(path).not_to exist
     end
@@ -218,6 +216,7 @@ describe Homebrew::Cleanup do
     it "does not clean up logs less than 30 days old" do
       allow_any_instance_of(Pathname).to receive(:ctime).and_return(15.days.ago)
       allow_any_instance_of(Pathname).to receive(:mtime).and_return(15.days.ago)
+      path.mkpath
       subject.cleanup_logs
       expect(path).to exist
     end