Fix flow_gen.php to track https://phabricator.fb.com/D864123

A recent diff broke this test. Fixing it up... the issue was that a codegen change altered the number of instructions in Continuation::send().

hphp/test/quick/debugger/flow_gen.php.expectf

@@ -51,6 +51,8 @@ Break at Continuation::send()
 step
 Break at Continuation::send()
 step
+Break at Continuation::send()
+step
 Break at genFoo$continuation() on line 11 of %s/flow_gen.php
   10 
   11 function genFoo($a) {
@@ -108,6 +110,8 @@ Break at Continuation::send()
 step
 Break at Continuation::send()
 step
+Break at Continuation::send()
+step
 Break at genFoo$continuation() on line 11 of %s/flow_gen.php
   10 
   11 function genFoo($a) {

hphp/test/quick/debugger/flow_gen.php.in

@@ -11,6 +11,7 @@ step
 step
 step
 step
+step
 next
 next
 next
@@ -21,6 +22,7 @@ step
 step
 step
 step
+step
 next
 next
 next