Remove pop_num from the validation algorithm

It was not used.

document/core/appendix/algorithm.rst

diff --git a/document/core/appendix/algorithm.rst b/document/core/appendix/algorithm.rst
index 3021408..cdbc318 100644
--- a/document/core/appendix/algorithm.rst
+++ b/document/core/appendix/algorithm.rst
@@ -188,11 +188,6 @@
      error_if(not matches_val(actual, expect))
      return actual
 
-   func pop_num() : num_type | Bot =
-     let actual = pop_val()
-     error_if(not is_num(actual))
-     return actual
-
    func pop_ref() : ref_type =
      let actual = pop_val()
      error_if(not is_ref(actual))