various: fix future tense in tests

Co-authored-by: Bo Anderson <mail@boanderson.me>

Library/Homebrew/test/cask/dsl_spec.rb

@@ -34,7 +34,7 @@ describe Cask::DSL, :cask do
       end.to output(expected).to_stderr
     end
 
-    it "will simply warn, not throw an exception" do
+    it "simply warns, instead of throwing an exception" do
       expect do
         attempt_unknown_method
       end.not_to raise_error

Library/Homebrew/test/cask/upgrade_spec.rb

@@ -476,7 +476,7 @@ describe Cask::Upgrade, :cask do
       allow_any_instance_of(described_class).to receive(:verbose?).and_return(true)
     end
 
-    it "will not end the upgrade process" do
+    it "does not end the upgrade process" do
       bad_checksum = Cask::CaskLoader.load("bad-checksum")
       bad_checksum_path = bad_checksum.config.appdir.join("Caffeine.app")
 

Library/Homebrew/test/completions_spec.rb

@@ -220,7 +220,7 @@ describe Homebrew::Completions do
         expect(described_class.command_options("help")).to eq({})
       end
 
-      it "will override global options with local descriptions" do
+      it "overrides global options with local descriptions" do
         options = described_class.command_options("upgrade")
         expect(options["--verbose"]).to eq "Print the verification and post-install steps."
       end