[turbofan] Rename {CheckPoint} to {Checkpoint} everywhere.

src/compiler/typer.cc

Index: src/compiler/typer.cc
diff --git a/src/compiler/typer.cc b/src/compiler/typer.cc
index afd09882830a479dcf69120cc3612fd19cc00893..29cbc57959e0ebd90ac0a926d9716809aa94459d 100644
--- a/src/compiler/typer.cc
+++ b/src/compiler/typer.cc
@@ -705,7 +705,7 @@ Type* Typer::Visitor::TypeTypeGuard(Node* node) {
   return Type::Intersect(input_type, guard_type, zone());
 }
 
-Type* Typer::Visitor::TypeCheckPoint(Node* node) {
+Type* Typer::Visitor::TypeCheckpoint(Node* node) {
   UNREACHABLE();
   return nullptr;
 }