template.c: simplify file_length calculation

src/template.c

@@ -241,18 +241,12 @@ main(void)
 
 	// 2. prepare variables
 	const uint32_t header_size =
-		4 * 4  /* 4 strings of 4 characters */ +
-		5 * 4  /* 5 uint32_t values */         +
+		3 * 4  /* 3 strings of 4 characters: "WAVE", "fmt ", "data" */ +
+		4 * 4  /* 4 uint32_t values */ +
 		4 * 2  /* 4 uint16_t values */;
 
 	uint32_t buffer_size = PRODUCT * (REPEAT_TIMES + 1),
-		file_length =
-			header_size +
-			buffer_size /* sample data */
-
-			/* subtract Subchunk2 headers: */
-			- 4 /* a string of 4 characters */
-			- 4 /* a uint32_t value */,
+		file_length = header_size + buffer_size,
 		fmt_data_length = 16 /* <--
 		 * length of format data before this value
 		 * in the file format structure