patch 8.2.3318: Vim9: cannot ignore quotes in number at the command line

Problem:    Vim9: cannot ignore quotes in number at the command line.
Solution:   Use in_vim9script() so that after ":vim9" quotes are ignored.
diff --git a/src/testdir/test_float_func.vim b/src/testdir/test_float_func.vim
index 628bbb0..77687d1 100644
--- a/src/testdir/test_float_func.vim
+++ b/src/testdir/test_float_func.vim
@@ -261,6 +261,10 @@
   call assert_fails("echo string(123'456.7'89)", 'E116:')
 enddef
 
+func Test_float_quotes_from_legacy()
+  call assert_equal("\n123456.789", execute("vim9 echo 12'34'56.789"))
+endfunc
+
 func Test_float2nr()
   call assert_equal(1, float2nr(1.234))
   call assert_equal(123, float2nr(1.234e2))