Fix typos

[Marcofann]

This PR corrects several typos in comments across multiple Rust files in the codebase. These changes improve readability and maintain consistency without affecting functionality.

Files and Changes:

• crates/relayer-cli/src/conclude.rs
  • Fixed "a error status" to "an error status."
• tools/integration-test/src/tests/client_upgrade.rs
  • Corrected "an chain upgrade proposal" to "a chain upgrade proposal."
• tools/test-framework/src/docs/walkthroughs/simple.rs
  • Fixed "an struct" to "a struct."
• tools/test-framework/src/types/tagged/dual.rs
  • Corrected "an result tagged value" to "a result tagged value."
• tools/test-framework/src/types/tagged/mono.rs
  • Corrected "an result tagged value" to "a result tagged value."