Removes unnecessary cwd and pipeline from various tests (#9202)

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Cleans up various tests that unnecessarily use the `cwd` argument of
`nu!`, and the `pipeline` function for single line commands. Also
replaces some unnecessary raw strings with normal strings. Part of
#8670.

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crates/nu-color-config/src/style_computer.rs

@@ -270,7 +270,7 @@ fn test_computable_style_closure_errors() {
         };"#,
         "[bell] | table",
     ];
-    let actual_repl = nu!(cwd: ".", nu_repl_code(&inp));
+    let actual_repl = nu!(nu_repl_code(&inp));
     // Check that the error was printed
     assert!(actual_repl.err.contains("type mismatch for operator"));
     // Check that the value was printed