Remove ICU4XError variants that are better modelled as Options (#4964)

Author: robertbastian

Cargo.lock

@@ -199,10 +199,10 @@ icu_benchmark_macros = { path = "tools/benchmark/macros" }
 
 # The version here can either be a `version = ".."` spec or `git = "https://github.com/rust-diplomat/diplomat", rev = ".."`
 # Diplomat must be published preceding a new ICU4X release but may use git versions in between
-diplomat = { git = "https://github.com/rust-diplomat/diplomat", rev = "950786dfea5cc5eb2c65eedee0bb013e8ee7a64e" }
-diplomat-runtime = { git = "https://github.com/rust-diplomat/diplomat", rev = "950786dfea5cc5eb2c65eedee0bb013e8ee7a64e" }
-diplomat_core = { git = "https://github.com/rust-diplomat/diplomat", rev = "950786dfea5cc5eb2c65eedee0bb013e8ee7a64e" }
-diplomat-tool = { git = "https://github.com/rust-diplomat/diplomat", rev = "950786dfea5cc5eb2c65eedee0bb013e8ee7a64e" }
+diplomat = { git = "https://github.com/rust-diplomat/diplomat", rev = "6aee3dbabea22ef8897af8b1e3635f98f5bd4a4f" }
+diplomat-runtime = { git = "https://github.com/rust-diplomat/diplomat", rev = "6aee3dbabea22ef8897af8b1e3635f98f5bd4a4f" }
+diplomat_core = { git = "https://github.com/rust-diplomat/diplomat", rev = "6aee3dbabea22ef8897af8b1e3635f98f5bd4a4f" }
+diplomat-tool = { git = "https://github.com/rust-diplomat/diplomat", rev = "6aee3dbabea22ef8897af8b1e3635f98f5bd4a4f" }
 
 # EXTERNAL DEPENDENCIES
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