Remove canStart from the docstrings

src/service.ts

@@ -173,7 +173,7 @@ export class DebugService implements IDebugger {
 
   /**
    * Starts a debugger.
-   * Precondition: canStart() && !isStarted()
+   * Precondition: !isStarted()
    */
   async start(): Promise<void> {
     await this.session.start();

src/tokens.ts

@@ -78,7 +78,7 @@ export interface IDebugger extends IDisposable {
 
   /**
    * Starts a debugger.
-   * Precondition: canStart() && !isStarted()
+   * Precondition: !isStarted()
    */
   start(): Promise<void>;