[Dylink] Remove a racy assertion (#13060)

If 2 side modules are loaded, A and B, and loadModule is called on A, then B,
then it is possible that if instantiation is done async here then the
postInstantiation() callbacks may happen in the reverse order, racily. If that
happens, the extra assertions on the table not changing can fire incorrectly -
the other parts of the table will appear to have changed meanwhile, but for
valid reasons.

Fixes #13054
Fixes #11458

src/library_dylink.js

diff --git a/src/library_dylink.js b/src/library_dylink.js
index 583e3fe..55e2501 100644
--- a/src/library_dylink.js
+++ b/src/library_dylink.js
@@ -395,22 +395,12 @@
         'env': proxy,
         {{{ WASI_MODULE_NAME }}}: proxy,
       };
-#if ASSERTIONS
-      var oldTable = [];
-      for (var i = 0; i < tableBase; i++) {
-        oldTable.push(table.get(i));
-      }
-#endif
 
       function postInstantiation(instance) {
 #if ASSERTIONS
         // the table should be unchanged
         assert(table === originalTable);
         assert(table === wasmTable);
-        // the old part of the table should be unchanged
-        for (var i = 0; i < tableBase; i++) {
-          assert(table.get(i) === oldTable[i], 'old table entries must remain the same');
-        }
         // verify that the new table region was filled in
         for (var i = 0; i < tableSize; i++) {
           assert(table.get(tableBase + i) !== undefined, 'table entry was not filled in');