Remove unnecessary test for availability of JSR-310 classes

We used to need this test when we supported Java 6 and 7,
but it's no longer needed with Java 8 as the minimum.

JAVA-4411

Author: jyemin

bson/src/main/org/bson/codecs/jsr310/Jsr310CodecProvider.java

@@ -41,15 +41,10 @@
 public class Jsr310CodecProvider implements CodecProvider {
     private static final Map<Class<?>, Codec<?>> JSR310_CODEC_MAP = new HashMap<Class<?>, Codec<?>>();
     static {
-        try {
-            Class.forName("java.time.Instant"); // JSR-310 support canary test.
-            putCodec(new InstantCodec());
-            putCodec(new LocalDateCodec());
-            putCodec(new LocalDateTimeCodec());
-            putCodec(new LocalTimeCodec());
-        } catch (ClassNotFoundException e) {
-            // No JSR-310 support
-        }
+        putCodec(new InstantCodec());
+        putCodec(new LocalDateCodec());
+        putCodec(new LocalDateTimeCodec());
+        putCodec(new LocalTimeCodec());
     }
 
     private static void putCodec(final Codec<?> codec) {