Remove adamv-alt references.

Closes Homebrew/homebrew#20364.

Library/Homebrew/cmd/update.rb

@@ -2,9 +2,6 @@ require 'cmd/tap'
 require 'cmd/untap'
 
 module Homebrew extend self
-
-  DEPRECATED_TAPS = ['adamv-alt']
-
   def update
     unless ARGV.named.empty?
       abort <<-EOS.undent
@@ -28,12 +25,6 @@ module Homebrew extend self
     Dir["Library/Taps/*"].each do |tapd|
       next unless File.directory?(tapd)
 
-      basename = Pathname.new(tapd).basename.to_s
-      if DEPRECATED_TAPS.include?(basename)
-        opoo "#{basename} is deprecated; please untap it"
-        next
-      end
-
       cd tapd do
         begin
           updater = Updater.new

Library/Homebrew/extend/pathname.rb

@@ -344,14 +344,6 @@ class Pathname
   end
 
   def find_formula
-    # remove special casing once tap is established and alt removed
-    if self == HOMEBREW_LIBRARY/"Taps/adamv-alt"
-      all_formula do |file|
-        yield file
-      end
-      return
-    end
-
     [self/:Formula, self/:HomebrewFormula, self].each do |d|
       if d.exist?
         d.children.map{ |child| child.relative_path_from(self) }.each do |pn|