Allows subroutine calls in return statments

[gabrielg]

Not sure why this check was added, but Fastly, as of writing, does allow subroutine calls in returns. For example, see these subroutines defined in init:

sub return_test_str STRING {
	return std.toupper("test");
}

sub return_test_bool BOOL {
	return randombool(1, 2);
}

These can be called from vcl_recv successfully like so:

declare local var.strret STRING;
declare local var.boolret BOOL;

set var.strret = return_test_str();
set var.boolret = return_test_bool();

log "testing returns: " var.strret ", " var.boolret;

Here's an example Fiddle: https://fiddle.fastly.dev/fiddle/b872e5de

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Has Fastly's behaviour perhaps changed recently and Falco is reflecting a previous behaviour?