Update thiserror requirement from 1.0 to 2.0 #1252

Job	Run time
tests-argmin-checkpointing-file	29s
tests-argmin	3m 53s
tests-argmin-observer-paramwriter	28s
tests-argmin-serde1-feature	2m 27s
tests-argmin-observer-slog	42s
clippy	3m 36s
docs-build	47s
cargo-deny (advisories)	29s
rustfmt	26s
cargo-deny (bans licenses sources)	31s
tests-argmin-math	4m 3s
tests-argmin-observer-spectator	2m 0s
tests-argmin-testfunctions	48s
tests-finitediff	30s
wasm-build	1m 1s
	22m 10s

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