clippy: remove match_on_vec_items

This would warn about some subset of index-related panics. In recent
nightlies this has been subsumed by the `indexing_slicing` lint which
lints on all array indexing. This is pretty cool but waay overkill.

Author: apoelstra

Cargo.toml

@@ -44,6 +44,7 @@ exclude = ["fuzz", "bitcoind-tests"]
 large_enum_variant = "allow" # docs say "measure before paying attention to this"; why is it on by default??
 similar_names = "allow" # Too many (subjectively) false positives.
 uninlined_format_args = "allow" # This is a subjective style choice.
+indexing_slicing = "allow" # Too many false positives ... would be cool though
 match_bool = "allow" # Adds extra indentation and LOC.
 match_same_arms = "allow" # Collapses things that are conceptually unrelated to each other.
 must_use_candidate = "allow" # Useful for audit but many false positives.
@@ -107,7 +108,6 @@ manual_ok_or = "warn"
 manual_string_new = "warn"
 many_single_char_names = "warn"
 map_unwrap_or = "allow"
-match_on_vec_items = "warn"
 match_wild_err_arm = "warn"
 match_wildcard_for_single_variants = "allow"
 maybe_infinite_iter = "warn"