Rename longest_chain to longestChain for convention

lean/Spa/Lattice.lean

@@ -58,7 +58,7 @@ structure PointedLTSeries (α : Type*) (f t : α)(n : ℕ) [Preorder α] where
 
 class FiniteHeightLattice (α : Type*) [Lattice α] extends Bot α, Top α where
   height : ℕ
-  longest_chain : PointedLTSeries α ⊥ ⊤ height
+  longestChain : PointedLTSeries α ⊥ ⊤ height
   chains_bounded : BoundedChains α height
 
 namespace FixedHeight
@@ -70,7 +70,7 @@ theorem bot_le [FiniteHeightLattice α] : ∀ (a : α), ⊥ ≤ a := by
   by_cases heq : ⊥ ⊓ a = ⊥
   · exact inf_eq_left.mp heq
   · exfalso
-    have lc := FiniteHeightLattice.longest_chain (α := α)
+    have lc := FiniteHeightLattice.longestChain (α := α)
     have hlt : ⊥ ⊓ a < lc.series.head := by
       rw [lc.head_series]
       exact lt_of_le_of_ne inf_le_left heq