Consider removing default shielding memo value

[HonzaR]

Is your feature request related to a problem? Please describe.

Current API:

    suspend fun shieldFunds(
        usk: UnifiedSpendingKey,
        memo: String = ZcashSdk.DEFAULT_SHIELD_FUNDS_MEMO_PREFIX
    ): Long

    /**
     * The default memo to use when shielding transparent funds.
     */
    const val DEFAULT_SHIELD_FUNDS_MEMO_PREFIX = "shielding:"

Describe the solution you'd like

Alternatives you've considered

Additional context

[HonzaR]

@nuttycom We want to remove the default memo value in the shielding transparent funds API, even though it can be easily overridden with "". Is that correct? Thank you.

[nuttycom]

I'm not sure what this request was related to; allowing a memo when shielding is an important use case, so this shouldn't be a change at the level of the SDK. Shielding memos are well supported by zcash_client_backend.

[HonzaR]

My question is only about the default string prefix of value of the memo parameter.

[nuttycom]

My question is only about the default string prefix of value of the memo parameter.

I'm not sure where that convention came from; it certainly wasn't something that we discussed for ZIP 316.