Correct typos and formatting in listing 3.6

src/chapter-03.md

@@ -1932,14 +1932,14 @@ timing.
 ;
 ; By Michael Abrash
 ;
-mystack   segment    para stack ‘STACK'
+mystack   segment    para stack 'STACK'
      db         512 dup(?)
 mystack   ends
 ;
-Code  segment   para public ‘CODE'
+Code  segment   para public 'CODE'
       assume    cs:Code, ds:Code
       extrn     ZTimerOn:near, ZTimerOff:near, ZTimerReport:near
-Startproc   near
+Start proc near
      push  cs
      pop   ds      ;point DS to the code segment,
                    ; so data as well as code can easily