doc: remove json quoting from gettxoutsetinfo and getblockstats cli examples #36155

This is a followup change based on #33230 (comment) because #33230 enabled handling cli arguments with either json or a string but the examples (i.e. bitcoin-cli help gettxoutsetinfo and bitcoin-cli help getblockstats) left the quotes. I considered adding a new example but felt that change might seem confusing.

Steps used for building and verifying

cmake -B build --fresh -DBUILD_KERNEL_LIB=ON -DBUILD_KERNEL_TEST=ON -DENABLE_IPC=OFF

./build/bin/bitcoind -regtest -daemon -coinstatsindex

# after "synced" is true via ./build/bin/bitcoin-cli -regtest -rpcwait getindexinfo

./build/bin/bitcoin-cli -regtest help gettxoutsetinfo

# example now reads: bitcoin-cli gettxoutsetinfo "none" 00000000c937983704a73af28acdec37b049d214adbda81d7e2a3dd146f6ed09

./build/bin/bitcoin-cli -regtest help getblockstats

# example now reads: bitcoin-cli getblockstats 00000000c937983704a73af28acdec37b049d214adbda81d7e2a3dd146f6ed09 '["minfeerate","avgfeerate"]'

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Code Coverage & Benchmarks

For details see: https://corecheck.dev/bitcoin/bitcoin/pulls/36155.

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