behavior: import unintentionally excluded file from behavior.zig

And remove the now-invalid test for the return value of `@branchHint`.

test/behavior.zig

@@ -12,6 +12,7 @@ test {
     _ = @import("behavior/bitcast.zig");
     _ = @import("behavior/bitreverse.zig");
     _ = @import("behavior/bool.zig");
+    _ = @import("behavior/builtin_functions_returning_void_or_noreturn.zig");
     _ = @import("behavior/byteswap.zig");
     _ = @import("behavior/byval_arg_var.zig");
     _ = @import("behavior/call.zig");

test/behavior/builtin_functions_returning_void_or_noreturn.zig

@@ -22,7 +22,6 @@ test {
     try testing.expectEqual(noreturn, @TypeOf(if (true) @panic("") else {}));
     try testing.expectEqual({}, @prefetch(&val, .{}));
     try testing.expectEqual({}, @setAlignStack(16));
-    try testing.expectEqual({}, @branchHint(.cold));
     try testing.expectEqual({}, @setEvalBranchQuota(0));
     try testing.expectEqual({}, @setFloatMode(.optimized));
     try testing.expectEqual({}, @setRuntimeSafety(true));