Rename the getter method [getPublickKey()]

[umang8496]

reference-implementations/utilities/on_subscibe-service/java/src/main/java/ondc/onboarding/utility/CryptoKeyPair.java

Line 27 in c0c5f88

public byte[] getPublickKey() {

Rename this to getPublicKey(). Also modify the references of this method.

[umang8496]

For reference: #82