Disable no-non-null assertions lint rule (#8699)

This *allows* us to use `variable!.prop` to ensure `variable` is not null/undefined.

.eslintrc.js

@@ -115,6 +115,8 @@ module.exports = {
                 "@typescript-eslint/no-explicit-any": "off",
                 // We'd rather not do this but we do
                 "@typescript-eslint/ban-ts-comment": "off",
+                // We're okay with assertion errors when we ask for them
+                "@typescript-eslint/no-non-null-assertion": "off",
             },
         },
         // temporary override for offending icon require files