remove problematic bigint optimisation (FasterXML#987)

Author: pjfanning

src/main/java/com/fasterxml/jackson/core/io/NumberInput.java

@@ -8,10 +8,6 @@
 
 public final class NumberInput
 {
-    // numbers with more than these characters are better parsed with BigDecimalParser
-    // parsing numbers with many digits in Java is slower than O(n)
-    private final static int LARGE_INT_SIZE = 1250;
-
     /**
      * Formerly used constant for a value that was problematic on certain
      * pre-1.8 JDKs.
@@ -398,10 +394,7 @@ public static BigDecimal parseBigDecimal(char[] ch) throws NumberFormatException
      * @throws NumberFormatException if string cannot be represented by a BigInteger
      * @since v2.14
      */
-    public static BigInteger parseBigInteger(String s) throws NumberFormatException {
-        if (s.length() > LARGE_INT_SIZE) {
-            return BigDecimalParser.parse(s).toBigInteger();
-        }
+    public static BigInteger parseBigInteger(final String s) throws NumberFormatException {
         return new BigInteger(s);
     }
 }