diagnostic: remove check_user_curlrc check.

Library/Homebrew/diagnostic.rb

@@ -480,21 +480,6 @@ module Homebrew
         EOS
       end
 
-      def check_user_curlrc
-        curlrc_found = %w[CURL_HOME HOME].any? do |var|
-          ENV[var] && File.exist?("#{ENV[var]}/.curlrc")
-        end
-        return unless curlrc_found
-
-        <<~EOS
-          You have a curlrc file
-          If you have trouble downloading packages with Homebrew, then maybe this
-          is the problem? If the following command doesn't work, then try removing
-          your curlrc:
-            curl #{Formatter.url("https://github.com")}
-        EOS
-      end
-
       def check_for_gettext
         find_relative_paths("lib/libgettextlib.dylib",
                             "lib/libintl.dylib",

Library/Homebrew/test/diagnostic_spec.rb

@@ -131,15 +131,6 @@ describe Homebrew::Diagnostic::Checks do
     end
   end
 
-  specify "#check_user_curlrc" do
-    mktmpdir do |path|
-      FileUtils.touch "#{path}/.curlrc"
-      ENV["CURL_HOME"] = path
-
-      expect(subject.check_user_curlrc).to match("You have a curlrc file")
-    end
-  end
-
   specify "#check_for_config_scripts" do
     mktmpdir do |path|
       file = "#{path}/foo-config"

Library/Homebrew/test/utils/curl_spec.rb

@@ -2,9 +2,14 @@ require "utils/curl"
 
 describe "curl" do
   describe "curl_args" do
-    it "returns -q as the first argument" do
+    it "returns -q as the first argument when HOMEBREW_CURLRC is set" do
+      ENV["HOMEBREW_CURLRC"] = "1"
       # -q must be the first argument according to "man curl"
       expect(curl_args("foo")[1]).to eq("-q")
     end
+
+    it "doesn't return -q as the first argument when HOMEBREW_CURLRC is not set" do
+      expect(curl_args("foo")[1]).to_not eq("-q")
+    end
   end
 end