udpate rust toolchain to rust 1.81.0 (#14473)

# Description

With the release of rust 1.83.0 it's time to update to rust 1.81.0.

crates/nu-parser/src/parse_patterns.rs

@@ -1,3 +1,5 @@
+#![allow(clippy::byte_char_slices)]
+
 use crate::{
     lex, lite_parse,
     parser::{is_variable, parse_value},
@@ -7,7 +9,6 @@ use nu_protocol::{
     engine::StateWorkingSet,
     ParseError, Span, SyntaxShape, Type, VarId,
 };
-
 pub fn garbage(span: Span) -> MatchPattern {
     MatchPattern {
         pattern: Pattern::Garbage,

crates/nu-parser/src/parse_shape_specs.rs

@@ -1,3 +1,5 @@
+#![allow(clippy::byte_char_slices)]
+
 use crate::{lex::lex_signature, parser::parse_value, trim_quotes, TokenContents};
 use nu_protocol::{engine::StateWorkingSet, ParseError, Span, SyntaxShape, Type};
 

crates/nu-parser/src/parser.rs

@@ -1,3 +1,5 @@
+#![allow(clippy::byte_char_slices)]
+
 use crate::{
     lex::{is_assignment_operator, lex, lex_n_tokens, lex_signature, LexState},
     lite_parser::{lite_parse, LiteCommand, LitePipeline, LiteRedirection, LiteRedirectionTarget},