Remove migration of linuxbrew-core formulae

Follow up to #21190. We enabled migration over 4 years ago
since #12248, which was part of brew 3.3.0. So at least 2
major brew releases have passed and all active Linuxbrew users would
have been migrated already.

There are only 25 formulae left so anyone who hasn't migrated can just
reinstall formulae if impacted.

Author: cho-m

Library/Homebrew/cmd/update-report.rb

@@ -148,29 +148,6 @@ def output_update_report
           next if !tap.git? || tap.git_repository.origin_url.nil?
           next if (tap.core_tap? || tap.core_cask_tap?) && !Homebrew::EnvConfig.no_install_from_api?
 
-          if ENV["HOMEBREW_MIGRATE_LINUXBREW_FORMULAE"].present? && tap.core_tap? &&
-             Settings.read("linuxbrewmigrated") != "true"
-            ohai "Migrating formulae from linuxbrew-core to homebrew-core"
-
-            require "linuxbrew-core-migration"
-            LINUXBREW_CORE_MIGRATION_LIST.each do |name|
-              begin
-                formula = Formula[name]
-              rescue FormulaUnavailableError
-                next
-              end
-              next unless formula.any_version_installed?
-
-              keg = formula.installed_kegs.fetch(-1)
-              tab = keg.tab
-              # force a `brew upgrade` from the linuxbrew-core version to the homebrew-core version (even if lower)
-              tab.source["versions"]["version_scheme"] = -1
-              tab.write
-            end
-
-            Settings.write "linuxbrewmigrated", true
-          end
-
           begin
             reporter = Reporter.new(tap)
           rescue Reporter::ReporterRevisionUnsetError => e
@@ -251,7 +228,7 @@ def output_update_report
             end
           end
           puts if args.auto_update?
-        elsif !args.auto_update? && !ENV["HOMEBREW_UPDATE_FAILED"] && !ENV["HOMEBREW_MIGRATE_LINUXBREW_FORMULAE"]
+        elsif !args.auto_update? && !ENV["HOMEBREW_UPDATE_FAILED"]
           puts "Already up-to-date." unless args.quiet?
         end
 

Library/Homebrew/cmd/update.sh

@@ -674,13 +674,6 @@ EOS
      [[ "${HOMEBREW_CORE_DEFAULT_GIT_REMOTE}" != "${HOMEBREW_CORE_GIT_REMOTE}" ||
         -n "${HOMEBREW_LINUXBREW_CORE_MIGRATION}" ]]
   then
-    if [[ -n "${HOMEBREW_LINUXBREW_CORE_MIGRATION}" ]]
-    then
-      # This means a migration is needed (in case it isn't run this time)
-      safe_cd "${HOMEBREW_REPOSITORY}"
-      git config --bool homebrew.linuxbrewmigrated false
-    fi
-
     safe_cd "${HOMEBREW_CORE_REPOSITORY}"
     echo "HOMEBREW_CORE_GIT_REMOTE set: using ${HOMEBREW_CORE_GIT_REMOTE} as the Homebrew/homebrew-core Git remote."
     git remote set-url origin "${HOMEBREW_CORE_GIT_REMOTE}"
@@ -692,12 +685,6 @@ EOS
 
   safe_cd "${HOMEBREW_REPOSITORY}"
 
-  # This means a migration is needed but hasn't completed (yet).
-  if [[ "$(git config get --type=bool homebrew.linuxbrewmigrated 2>/dev/null)" == "false" ]]
-  then
-    export HOMEBREW_MIGRATE_LINUXBREW_FORMULAE=1
-  fi
-
   # This means the user has run `brew which-formula` before and we should fetch executables.txt
   if [[ "$(git config get --type=bool homebrew.commandnotfound 2>/dev/null)" == "true" ]]
   then
@@ -1056,7 +1043,6 @@ EOS
      [[ -n "${HOMEBREW_UPDATE_FAILED}" ]] ||
      [[ -n "${HOMEBREW_MISSING_REMOTE_REF_DIRS}" ]] ||
      [[ -n "${HOMEBREW_UPDATE_FORCE}" ]] ||
-     [[ -n "${HOMEBREW_MIGRATE_LINUXBREW_FORMULAE}" ]] ||
      [[ -d "${HOMEBREW_LIBRARY}/LinkedKegs" ]] ||
      [[ ! -f "${HOMEBREW_CACHE}/all_commands_list.txt" ]] ||
      [[ -n "${HOMEBREW_DEVELOPER}" && -z "${HOMEBREW_UPDATE_AUTO}" ]]