Fix code comments errors (#3190)

## Motivation

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## Proposal

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## Test Plan

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## Release Plan

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- Nothing to do / These changes follow the usual release cycle.
- These changes should be backported to the latest `devnet` branch, then
    - be released in a new SDK,
    - be released in a validator hotfix.
- These changes should be backported to the latest `testnet` branch,
then
    - be released in a new SDK,
    - be released in a validator hotfix.
- Backporting is not possible but we may want to deploy a new `devnet`
and release a new
      SDK soon.

## Links

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- [reviewer
checklist](https://github.com/linera-io/linera-protocol/blob/main/CONTRIBUTING.md#reviewer-checklist)

examples/agent/src/main.rs

@@ -112,7 +112,7 @@ fragment TypeRef on __Type {
 "#;
 
 const PREAMBLE: &str = r#"
-You are a bot that works interacts with the Linera blockchain via a Linera wallet.
+You are a bot that works and interacts with the Linera blockchain via a Linera wallet.
 
 Even though you're going to be using mostly GraphQL, try to use natural language as much as possible to speak to the user.
 

examples/matching-engine/src/lib.rs

@@ -102,7 +102,7 @@ impl PriceBid {
     }
 }
 
-/// We use the custom serialization for the PriceAsk so that the order of the serialization
+/// We use the custom serialization for the PriceBid so that the order of the serialization
 /// corresponds to the order of the Prices.
 impl CustomSerialize for PriceBid {
     fn to_custom_bytes(&self) -> Result<Vec<u8>, ViewError> {

linera-base/src/command.rs

@@ -1,7 +1,7 @@
 // Copyright (c) Zefchain Labs, Inc.
 // SPDX-License-Identifier: Apache-2.0
 
-//! Command functionality used for spanning child processes.
+//! Command functionality used for spawning child processes.
 
 use std::{
     path::{Path, PathBuf},