Address a grammar error in failed reasons.

An overlooked grammatical error occurred in exactly 1 (one) of the possible failure reasons when being verified for the voice gate system. This was unacceptable to the masses, so a swift correction has been added to address it, adding 1 (one) additional word to the listed reason.

bot/exts/moderation/voice_gate.py

@@ -22,7 +22,7 @@
 )
 
 MESSAGE_FIELD_MAP = {
-    "verified_at": f"have been verified for less {GateConf.minimum_days_verified} days",
+    "verified_at": f"have been verified for less than {GateConf.minimum_days_verified} days",
     "voice_banned": "have an active voice ban infraction",
     "total_messages": f"have sent less than {GateConf.minimum_messages} messages",
 }