Fix clippy warnings (upcoming) (#9282)

# Description

Fixes the clippy warnings we're about to get hit with next time we
upgrade Rust.

The big one was shrinking ShellError and related under 128 bytes.

# User-Facing Changes

Shouldn't notice much difference. In theory, we could see a tiny perf
improvement, but I didn't notice one.

# Tests + Formatting
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crates/nu-command/src/math/median.rs

@@ -85,9 +85,9 @@ pub fn median(values: &[Value], span: Span, head: &Span) -> Result<Value, ShellE
             if elem[0].partial_cmp(&elem[1]).is_none() {
                 return Err(ShellError::OperatorMismatch {
                     op_span: *head,
-                    lhs_ty: elem[0].get_type(),
+                    lhs_ty: elem[0].get_type().to_string(),
                     lhs_span: elem[0].span()?,
-                    rhs_ty: elem[1].get_type(),
+                    rhs_ty: elem[1].get_type().to_string(),
                     rhs_span: elem[1].span()?,
                 });
             }

crates/nu-command/src/math/mode.rs

@@ -104,9 +104,9 @@ pub fn mode(values: &[Value], _span: Span, head: &Span) -> Result<Value, ShellEr
             if elem[0].partial_cmp(&elem[1]).is_none() {
                 return Err(ShellError::OperatorMismatch {
                     op_span: *head,
-                    lhs_ty: elem[0].get_type(),
+                    lhs_ty: elem[0].get_type().to_string(),
                     lhs_span: elem[0].span()?,
-                    rhs_ty: elem[1].get_type(),
+                    rhs_ty: elem[1].get_type().to_string(),
                     rhs_span: elem[1].span()?,
                 });
             }

crates/nu-command/src/math/reducers.rs

@@ -41,9 +41,9 @@ pub fn max(data: Vec<Value>, span: Span, head: Span) -> Result<Value, ShellError
         } else {
             return Err(ShellError::OperatorMismatch {
                 op_span: head,
-                lhs_ty: biggest.get_type(),
+                lhs_ty: biggest.get_type().to_string(),
                 lhs_span: biggest.span()?,
-                rhs_ty: value.get_type(),
+                rhs_ty: value.get_type().to_string(),
                 rhs_span: value.span()?,
             });
         }
@@ -72,9 +72,9 @@ pub fn min(data: Vec<Value>, span: Span, head: Span) -> Result<Value, ShellError
         } else {
             return Err(ShellError::OperatorMismatch {
                 op_span: head,
-                lhs_ty: smallest.get_type(),
+                lhs_ty: smallest.get_type().to_string(),
                 lhs_span: smallest.span()?,
-                rhs_ty: value.get_type(),
+                rhs_ty: value.get_type().to_string(),
                 rhs_span: value.span()?,
             });
         }