Revert "Pipeline operators: && and ||" (#7452)

Reverts nushell/nushell#7448

Some surprising behavior in how we do this. For example:

```
〉if (true || false) { print "yes!" } else { print "no!" }
no!
〉if (true or false) { print "yes!" } else { print "no!" }
yes!
```

This means for folks who are using the old `||`, they possibly get the
wrong answer once they upgrade. I don't think we can ship with that as
it will catch too many people by surprise and just make it easier to
write buggy code.

crates/nu-cli/src/completions/completer.rs

@@ -127,6 +127,7 @@ impl NuCompleter {
                 match pipeline_element {
                     PipelineElement::Expression(_, expr)
                     | PipelineElement::Redirection(_, _, expr)
+                    | PipelineElement::And(_, expr)
                     | PipelineElement::Or(_, expr) => {
                         let flattened: Vec<_> = flatten_expression(&working_set, &expr);
                         let span_offset: usize = alias_offset.iter().sum();

crates/nu-cli/src/syntax_highlight.rs

@@ -232,6 +232,7 @@ fn find_matching_block_end_in_block(
             match e {
                 PipelineElement::Expression(_, e)
                 | PipelineElement::Redirection(_, _, e)
+                | PipelineElement::And(_, e)
                 | PipelineElement::Or(_, e) => {
                     if e.span.contains(global_cursor_offset) {
                         if let Some(pos) = find_matching_block_end_in_expr(