Replace FormulaTextAuditor usage

- Only two audits were using this: `audit_keg_only_reason` and `audit_text`,
  and they weren't using any of its text processing methods, so there's little
  reason to keep it around.
- The "`keg_only_reason` shouldn't contain 'HOMEBREW_PREFIX'" audit can easily
  be replaced with a RuboCop since that's "just" text parsing.
- The "tests should invoke binaries with `bin/<command>`" audit had to stay as
  a FormulaAudit because it requires accessing attributes about the Formula
  like its name, aliases, which RuboCop can't get to, but it was easy to move the
  singular "read the text in the file" line from `FormulaTextAuditor`.

Library/Homebrew/formula_auditor.rb

@@ -2,7 +2,6 @@
 # frozen_string_literal: true
 
 require "deprecate_disable"
-require "formula_text_auditor"
 require "formula_versions"
 require "resource_auditor"
 require "utils/shared_audits"
@@ -32,7 +31,7 @@ def initialize(formula, options = {})
       @core_tap = formula.tap&.core_tap? || options[:core_tap]
       @problems = []
       @new_formula_problems = []
-      @text = FormulaTextAuditor.new(formula.path)
+      @text = formula.path.open("rb", &:read)
       @specs = %w[stable head].filter_map { |s| formula.send(s) }
       @spdx_license_data = options[:spdx_license_data]
       @spdx_exception_data = options[:spdx_exception_data]
@@ -510,16 +509,6 @@ def audit_relicensed_formulae
               "It must not be upgraded to version #{relicensed_version} or newer."
     end
 
-    def audit_keg_only_reason
-      return unless @core_tap
-      return unless formula.keg_only?
-
-      keg_only_message = text.to_s.match(/keg_only\s+["'](.*)["']/)&.captures&.first
-      return unless keg_only_message&.include?("HOMEBREW_PREFIX")
-
-      problem "`keg_only` reason should not include `HOMEBREW_PREFIX` as it creates confusing `brew info` output."
-    end
-
     def audit_versioned_keg_only
       return unless @versioned_formula
       return unless @core_tap

Library/Homebrew/rubocops/text.rb

@@ -30,8 +30,15 @@ def audit_formula(node, _class_node, _parent_class_node, body_node)
             problem "Formulae should not depend on both OpenSSL and LibreSSL (even optionally)."
           end
 
-          if formula_tap == "homebrew-core" && (depends_on?("veclibfort") || depends_on?("lapack"))
-            problem "Formulae in homebrew/core should use OpenBLAS as the default serial linear algebra library."
+          if formula_tap == "homebrew-core"
+            if depends_on?("veclibfort") || depends_on?("lapack")
+              problem "Formulae in homebrew/core should use OpenBLAS as the default serial linear algebra library."
+            end
+
+            if find_node_method_by_name(body_node, :keg_only)&.source&.include?("HOMEBREW_PREFIX")
+              problem "`keg_only` reason should not include `HOMEBREW_PREFIX` " \
+                      "as it creates confusing `brew info` output."
+            end
           end
 
           unless method_called_ever?(body_node, :go_resource)

Library/Homebrew/test/formula_auditor_spec.rb

@@ -1238,7 +1238,7 @@ class FooAT11 < Formula
 
   describe "#audit_conflicts" do
     before do
-      # We don't really test FormulaTextAuditor here
+      # We don't really test the formula text retrieval here
       allow(File).to receive(:open).and_return("")
     end