HomebrewFormula: drop formula, now in Homebrew’s repository (#318)

* HomebrewFormula: drop formula, now in Homebrew’s repository
* doc: update brew install, tap not required

HomebrewFormula/age.rb

@@ -1,23 +0,0 @@
-# Copyright 2019 Google LLC
-#
-# Use of this source code is governed by a BSD-style
-# license that can be found in the LICENSE file or at
-# https://developers.google.com/open-source/licenses/bsd
-
-class Age < Formula
-  desc "Simple, modern, secure file encryption"
-  homepage "https://filippo.io/age"
-  url "https://github.com/FiloSottile/age/archive/v1.0.0-rc.3.zip"
-  sha256 "0e7d94f17e610d5ad9ce8e88e3c157b073dcc41984b1d07793aef44b9e3b67d8"
-  head "https://github.com/FiloSottile/age.git"
-
-  depends_on "go" => :build
-
-  def install
-    mkdir bin
-    system "go", "build", "-trimpath", "-o", bin, "-ldflags", "-X main.Version=v#{version}", "filippo.io/age/cmd/..."
-    prefix.install_metafiles
-    man1.install "doc/age.1"
-    man1.install "doc/age-keygen.1"
-  end
-end

README.md

@@ -139,7 +139,6 @@ Keep in mind that people might not protect SSH keys long-term, since they are re
     <tr>
         <td>Homebrew (macOS or Linux)</td>
         <td>
-            <code>brew tap filippo.io/age https://filippo.io/age</code><br>
             <code>brew install age</code>
         </td>
     </tr>