Unset HOMEBREW_NO_EMOJI for all tests.

Library/Homebrew/dev-cmd/tests.rb

@@ -40,6 +40,7 @@ module Homebrew
       ENV.delete("HOMEBREW_TEMP")
       ENV.delete("HOMEBREW_LINKAGE_CACHE")
       ENV.delete("HOMEBREW_NO_GITHUB_API")
+      ENV.delete("HOMEBREW_NO_EMOJI")
       ENV["HOMEBREW_NO_ANALYTICS_THIS_RUN"] = "1"
       ENV["HOMEBREW_DEVELOPER"] = "1"
       ENV["HOMEBREW_NO_COMPAT"] = "1" if args.no_compat?

Library/Homebrew/test/emoji_spec.rb

@@ -5,7 +5,6 @@ describe Emoji do
     subject { described_class.install_badge }
 
     before do
-      ENV.delete("HOMEBREW_NO_EMOJI")
       ENV.delete("HOMEBREW_INSTALL_BADGE")
     end
 

Library/Homebrew/test/utils_spec.rb

@@ -32,8 +32,6 @@ describe "globally-scoped helper methods" do
       before { allow($stdout).to receive(:tty?).and_return(true) }
 
       context "with HOMEBREW_NO_EMOJI unset" do
-        before { ENV.delete("HOMEBREW_NO_EMOJI") }
-
         it "returns a string with a colored checkmark" do
           expect(subject)
             .to match(/#{esc 1}foo #{esc 32}✔#{esc 0}/)
@@ -66,8 +64,6 @@ describe "globally-scoped helper methods" do
       before { allow($stdout).to receive(:tty?).and_return(true) }
 
       context "with HOMEBREW_NO_EMOJI unset" do
-        before { ENV.delete("HOMEBREW_NO_EMOJI") }
-
         it "returns a string with a colored checkmark" do
           expect(subject)
             .to match(/#{esc 1}foo #{esc 31}✘#{esc 0}/)