PROHIBITION OF DISCRIMINATION IN PRACTICE LAW COMPETITION (DECISION ANALYSIS CASE NUMBER: 22/KPPU-L/2005 PRACTICE OF DISCRIMINATION BY PGN) LARANGAN PRAKTEK DISKRIMINASI DALAM HUKUM PERSAINGAN USAHA (ANALISA PUTUSAN PERKARA NOMOR: 22/KPPU-L/2005 TERHADAP PRAKTEK DISKRIMINASI OLEH PGN)