patch 8.2.3017: Vim9: debugger shows too many lines

Problem:    Vim9: debugger shows too many lines.
Solution:   Truncate at a comment, "enddef", etc. (closes #8392)
diff --git a/src/testdir/test_debugger.vim b/src/testdir/test_debugger.vim
index a6e3966..411909d 100644
--- a/src/testdir/test_debugger.vim
+++ b/src/testdir/test_debugger.vim
@@ -958,6 +958,10 @@
          a: 1,
          b: 2,
          }
+         # comment
+         def Inner()
+           eval 1
+         enddef
     enddef
   END
   call writefile(file, 'Xtest.vim')
@@ -997,6 +1001,7 @@
                 \ ':debug call FuncWithDict()',
                 \ ['cmd: call FuncWithDict()'])
   call RunDbgCmd(buf, 'step', ['line 1: var d = {  a: 1,  b: 2,  }'])
+  call RunDbgCmd(buf, 'step', ['line 6: def Inner()'])
 
   call RunDbgCmd(buf, 'cont')
   call StopVimInTerminal(buf)