[debugger] Remove obsolete stepping modes.

src/debug/debug.h

Index: src/debug/debug.h
diff --git a/src/debug/debug.h b/src/debug/debug.h
index d8e7596a9b53dca5319a0a0a4d2c5258273f7846..687a843e1a8730d1a05a06c53fb360a34c71b12b 100644
--- a/src/debug/debug.h
+++ b/src/debug/debug.h
@@ -37,10 +37,7 @@ enum StepAction {
   StepNext = 1,   // Step to the next statement in the current function.
   StepIn = 2,     // Step into new functions invoked or the next statement
                   // in the current function.
-  StepMin = 3,    // Perform a minimum step in the current function.
-  StepInMin = 4,  // Step into new functions invoked or perform a minimum step
-                  // in the current function.
-  StepFrame = 5   // Step into a new frame or return to previous frame.
+  StepFrame = 3   // Step into a new frame or return to previous frame.
 };