rpc: fix broken RPCExamples for waitforblock(height) #18398

This PR fixes several broken RPCExamples from the "blockchain" category:

• HelpExampleCli for waitforblock (disturbing comma between arguments)
• HelpExampleCli for waitforblockheight (disturbing comma between arguments)
• HelpExampleRpc for waitforblockheight (disturbing quotation marks around integer argument)

Note that the CLI example for waitforblockheight would also work with the first argument in quotation marks (in contrast to the RPC example), but I removed them as well as they are not needed.

Outputs for the non-working examples in the master branch:

$ ./bitcoin-cli waitforblock "0000000000079f8ef3d2c688c244eb7a4570b24c9ed7b4a8c619eb02596f8862", 1000
error code: -8
error message:
blockhash must be of length 64 (not 65, for '0000000000079f8ef3d2c688c244eb7a4570b24c9ed7b4a8c619eb02596f8862,')

$ ./bitcoin-cli waitforblockheight "100", 1000
error: Error parsing JSON:100,

$ curl --user __cookie__ --data-binary '{"jsonrpc": "1.0", "id": "curltest", "method": "waitforblockheight", "params": ["100", 1000]}' -H 'content-type: text/plain;' http://127.0.0.1:8332/
Enter host password for user '__cookie__':
{"result":null,"error":{"code":-1,"message":"JSON value is not an integer as expected"},"id":"curltest"}

Outputs for the fixed examples in the PR branch:

$ ./bitcoin-cli waitforblock "0000000000079f8ef3d2c688c244eb7a4570b24c9ed7b4a8c619eb02596f8862" 1000
{
  "hash": "0000000000000000000910ae4d56120e0ddd55c0552e80ed12dba147abc68080",
  "height": 622416
}

$ ./bitcoin-cli waitforblockheight 100 1000
{
  "hash": "0000000000000000000910ae4d56120e0ddd55c0552e80ed12dba147abc68080",
  "height": 622416
}

$ curl --user __cookie__ --data-binary '{"jsonrpc": "1.0", "id": "curltest", "method": "waitforblockheight", "params": [100, 1000]}' -H 'content-type: text/plain;' http://127.0.0.1:8332/
Enter host password for user '__cookie__':
{"result":{"hash":"0000000000000000000910ae4d56120e0ddd55c0552e80ed12dba147abc68080","height":622416},"error":null,"id":"curltest"}

ACK ef35604c9c88e7800e9be106b791b1c0fa8b310a

master:

src/bitcoin-cli waitforblock "0000000000079f8ef3d2c688c244eb7a4570b24c9ed7b4a8c619eb02596f8862", 1000
error code: -8
error message:
blockhash must be of length 64 (not 65, for '0000000000079f8ef3d2c688c244eb7a4570b24c9ed7b4a8c619eb02596f8862,')

src/bitcoin-cli waitforblockheight "100", 1000
error: Error parsing JSON:100,

PR:

src/bitcoin-cli waitforblock "0000000000079f8ef3d2c688c244eb7a4570b24c9ed7b4a8c619eb02596f8862" 1000
{
  "hash": "000000000000000000047fb670bd469bfcaa15fc8085c6befbda345b5348a167",
  "height": 622876
}

src/bitcoin-cli waitforblockheight 100 1000
{
  "hash": "000000000000000000047fb670bd469bfcaa15fc8085c6befbda345b5348a167",
  "height": 622876
}