Revert "Show original string byte sequence to debug"

This reverts commit b42fe5937a.

lib/irb/completion.rb

@@ -194,8 +194,6 @@ module IRB
           ":" + s.id2name.encode(Encoding.default_external)
         rescue EncodingError
           # ignore
-        rescue Encoding::InvalidByteSequenceError => e
-          raise "Invalid byte sequence #{s.id2name.bytes.inspect} #{e.inspect}"
         end
         candidates.grep(/^#{Regexp.quote(sym)}/)