Inflict Light Wounds is listed in the 3.5e PHB as a Necromancy spell but with no alignment descriptor at all. I cannot find anything in the PHB that prevents a Good-aligned Cleric from preparing that spell, even if they cannot cast it spontaneously. Is there some RAW somewhere else that prevents Good clerics from using unaligned Cleric spells from the Necromancy school?
You can prepare any of the inflict wounds spells as a Good Aligned Cleric, because they do not have the Evil descriptor. What you can't do is spontaneously cast your prepared spells as inflict wounds spells in the same way that you can do that for cure wounds spells. It doesn't have anything to do with the Necromancy school of magic. The Necromancy school is not necessarily Evil, so there is no alignment restriction for casting Necromancy Spells.
There is no prohibition to my knowledge.
I believe the citation you're thinking of is:
Chaotic, Evil, Good, and Lawful Spells A cleric can’t cast spells of an alignment opposed to his own or his deity’s (if he has one). Spells associated with particular alignments are indicated by the chaos, evil, good, and law descriptors in their spell descriptions.
Interestingly, per letter of the rules I read, a good cleric could even prepare evil spells, though couldn't cast them.