fix: update SignerMessage deserializing #1576

Job	Run time
test (cli, redis_tests)	11m 32s
distributions (ubuntu-latest, linux, x86_64-unknown-linux-gnu, x64, glibc)	10m 56s
test (sdk, stacks-signers)	7m 57s
distributions (windows-latest, windows, x86_64-pc-windows-msvc, x64)	11m 17s
distributions (macos-latest, darwin, x86_64-apple-darwin, x64)	7m 37s
distributions (macos-latest, darwin, aarch64-apple-darwin, arm64)	9m 45s
semantic-release	1s
build-publish	1s
deploy-dev	1s
auto-approve-dev	1s
deploy-staging	1s
auto-approve-stg	1s
deploy-prod	1s
	59m 11s

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