docs: Use of $any() has no runtime incidence. (#48785)

Some users are woried about `$any()` as function calls are to be avoided in templates. This sentence clarifies the situation.

fixes #48781

PR Close #48785

aio/content/guide/template-expression-operators.md

@@ -59,6 +59,8 @@ The `$any()` cast function also works with `this` to allow access to undeclared
 
 The `$any()` cast function works anywhere in a binding expression where a method call is valid.
 
+Also note that `$any()` only affects the typing. There is no method call in the generated code; the `$any()` function is entirely compiled away.
+
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