android: Change SHA of a string to return hex

This makes the API the same as iOS which returns hex when the
input is a string. This discrepancy has been around for a long
time and may break things for some people.

Author: cjthompson

android/src/main/java/com/pedrouid/crypto/RCTSha.java

@@ -87,7 +87,7 @@ public void shaBase64(String data, String algorithm, Promise promise) throws Exc
     public void shaUtf8(String data, String algorithm, Promise promise) throws Exception {
         try {
             byte[] digest = this.sha(data.getBytes(), algorithm);
-            promise.resolve(Base64.encodeToString(digest, Base64.DEFAULT));
+            promise.resolve(Util.bytesToHex(digest));
         } catch (Exception e) {
             promise.reject("-1", e.getMessage());
         }