: rename state argument to err in tridiagonal syntax

Author: srinjoy933

doc/specs/stdlib_specialmatrices.md

@@ -68,9 +68,10 @@ Tridiagonal matrices are available with all supported data types as `tridiagonal
 
 - To construct a tridiagonal matrix of size `n x n` with constant diagonal elements `dl`, `dv`, and `du`:
 
-`A = ` [[stdlib_specialmatrices(module):tridiagonal(interface)]] `(dl, dv, du, n [, state])`
+`A = ` [[stdlib_specialmatrices(module):tridiagonal(interface)]] `(dl, dv, du, n [, err])`
+
+Where `err` is an optional `intent(out)` argument of type `linalg_state_type`. When `state` is not present, the corresponding `tridiagonal` call is `pure` and signals invalid sizes or array shape mismatches via an internal `error stop`. When `state` is present, the impure overload is used instead, and any such error is reported by setting the `state` variable rather than executing an `error stop`.
 
-Where `state` is an optional `intent(out)` argument of type `linalg_state_type`. When `state` is not present, the corresponding `tridiagonal` call is `pure` and signals invalid sizes or array shape mismatches via an internal `error stop`. When `state` is present, the impure overload is used instead, and any such error is reported by setting the `state` variable rather than executing an `error stop`.
 
 #### Example