tests: sprintf: Fix incorrect message for 1234.56789 test

This commit fixes the test message showing an incorrect input value of
-1 when the actual input value is 1234.56789.

Signed-off-by: Stephanos Ioannidis <root@stephanos.io>

tests/lib/sprintf/src/main.c

@@ -255,7 +255,7 @@ void test_sprintf_double(void)
 	var.d = 1234.56789;
 	sprintf(buffer, "%f", var.d);
 	zassert_true((strcmp(buffer, "1234.567890") == 0),
-		     "sprintf(-1.0) - incorrect output '%s'\n", buffer);
+		     "sprintf(1234.56789) - incorrect output '%s'\n", buffer);
 
 	/*
 	 * With very large precision, the output differs significantly in