Fix rule for Sindarin initial ⟨i⟩

Sindarin ⟨i⟩ is only pronounced like ⟨j⟩ before another vowel and *at
the beginning of a word*. “Galadriel” does not have a /j/ sound.

dictsource/sjn_rules

@@ -32,7 +32,7 @@
 
 .group i
 	i	i
-	i (A	j
+	_) i (A	j
 
 // j and k do not occur in Sindarin