fix: wrong codegen name for a few resources

Author: sorccu

Diff for: packages/cli/src/constructs/heartbeat-check.codegen.ts

@@ -7,7 +7,7 @@ export interface HeartbeatCheckResource extends CheckResource {
   heartbeat: Heartbeat,
 }
 
-export function source (program: Program, logicalId: string, resource: HeartbeatCheckResource): void {
+export function codegen (program: Program, logicalId: string, resource: HeartbeatCheckResource): void {
   program.import('HeartbeatCheck', 'checkly/constructs')
 
   program.section(expr(ident('HeartbeatCheck'), builder => {

Diff for: packages/cli/src/constructs/multi-step-check.codegen.ts

@@ -11,7 +11,7 @@ export interface MultiStepCheckResource extends CheckResource {
 
 const construct = 'MultiStepCheck'
 
-export function source (program: Program, logicalId: string, resource: MultiStepCheckResource): void {
+export function codegen (program: Program, logicalId: string, resource: MultiStepCheckResource): void {
   program.import(construct, 'checkly/constructs')
 
   program.section(expr(ident(construct), builder => {