Remove file accidentally re-introduced by merge (#14785)

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# Description
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Re-removes the tests for `split_by`, which was removed in #14726 and
accidentally re-introduced by #14741

cc @fdncred 

# User-Facing Changes
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crates/nu-command/tests/commands/split_by.rs

@@ -1,61 +0,0 @@
-use nu_test_support::fs::Stub::EmptyFile;
-use nu_test_support::playground::Playground;
-use nu_test_support::{nu, pipeline};
-
-#[test]
-fn splits() {
-    let sample = r#"
-                [[first_name, last_name, rusty_at, type];
-                 [Andrés, Robalino, "10/11/2013", A],
-                 [JT, Turner, "10/12/2013", B],
-                 [Yehuda, Katz, "10/11/2013", A]]
-            "#;
-
-    let actual = nu!(pipeline(&format!(
-        r#"
-                  {sample}
-                | group-by rusty_at
-                | split-by type
-                | get A."10/11/2013"
-                | length
-            "#
-    )));
-
-    assert_eq!(actual.out, "2");
-}
-
-#[test]
-fn errors_if_no_input() {
-    Playground::setup("split_by_no_input", |dirs, _sandbox| {
-        let actual = nu!(cwd: dirs.test(), pipeline("split-by type"));
-
-        assert!(actual.err.contains("no input value was piped in"));
-    })
-}
-
-#[test]
-fn errors_if_non_record_input() {
-    Playground::setup("split_by_test_2", |dirs, sandbox| {
-        sandbox.with_files(&[
-            EmptyFile("los.txt"),
-            EmptyFile("tres.txt"),
-            EmptyFile("amigos.txt"),
-            EmptyFile("arepas.clu"),
-        ]);
-
-        let input_mismatch = nu!(cwd: dirs.test(), pipeline("5 | split-by type"));
-
-        assert!(input_mismatch.err.contains("doesn't support int input"));
-
-        let only_supports = nu!(
-            cwd: dirs.test(), pipeline(
-            "
-                ls
-                | get name
-                | split-by type
-            "
-        ));
-
-        assert!(only_supports.err.contains("Input type not supported"));
-    })
-}