test(log): cleaunp TextDecoder use (denoland#5407)

tests(log): cleaunp `TextDecoder` use

Author: iuioiua

log/file_handler_test.ts

@@ -12,9 +12,7 @@ Deno.test({
     class TestFileHandler extends FileHandler {
       override flush() {
         super.flush();
-        const decoder = new TextDecoder("utf-8");
-        const data = Deno.readFileSync(LOG_FILE);
-        const text = decoder.decode(data);
+        const text = Deno.readTextFileSync(LOG_FILE);
         assertEquals(text.slice(-1), "\n");
       }
 

log/rotating_file_handler_test.ts

@@ -204,20 +204,10 @@ Deno.test({
     ); // 'ERROR AAA\n' = 10 bytes
     fileHandler.destroy();
 
-    const decoder = new TextDecoder();
-    assertEquals(decoder.decode(Deno.readFileSync(LOG_FILE)), "ERROR AAA\n");
-    assertEquals(
-      decoder.decode(Deno.readFileSync(LOG_FILE + ".1")),
-      "original log file",
-    );
-    assertEquals(
-      decoder.decode(Deno.readFileSync(LOG_FILE + ".2")),
-      "original log.1 file",
-    );
-    assertEquals(
-      decoder.decode(Deno.readFileSync(LOG_FILE + ".3")),
-      "original log.2 file",
-    );
+    assertEquals(Deno.readTextFileSync(LOG_FILE), "ERROR AAA\n");
+    assertEquals(Deno.readTextFileSync(LOG_FILE + ".1"), "original log file");
+    assertEquals(Deno.readTextFileSync(LOG_FILE + ".2"), "original log.1 file");
+    assertEquals(Deno.readTextFileSync(LOG_FILE + ".3"), "original log.2 file");
     assert(!existsSync(LOG_FILE + ".4"));
 
     Deno.removeSync(LOG_FILE);