Remove legacy port file from LSP reporter (#3608)

### Motivation

Enough time has passed and the upgrades must have rolled out already. This PR removes support for the old port file, which has been replaced with the JSON DB.

Author: vinistock

lib/ruby_lsp/test_reporters/lsp_reporter.rb

@@ -20,8 +20,6 @@ def initialize
       dir_path = File.join(Dir.tmpdir, "ruby-lsp")
       FileUtils.mkdir_p(dir_path)
 
-      # Remove in 1 month once updates have rolled out
-      legacy_port_path = File.join(dir_path, "test_reporter_port")
       port_db_path = File.join(dir_path, "test_reporter_port_db.json")
       port = ENV["RUBY_LSP_REPORTER_PORT"]
 
@@ -32,8 +30,6 @@ def initialize
         elsif File.exist?(port_db_path)
           db = JSON.load_file(port_db_path)
           TCPSocket.new("localhost", db[Dir.pwd])
-        elsif File.exist?(legacy_port_path)
-          TCPSocket.new("localhost", File.read(legacy_port_path))
         else
           # For tests that don't spawn the TCP server
           require "stringio"