allow export alias in repl (#15054)

# Description
Fixes: #15048
The issue is happened while `parse_export_in_block`, it makes a call to
`parse_internal_call`, which may be an error.
But in reality, these errors are not useful, all useful errors will be
generated by `parse_xxx` at the end of the function.

# User-Facing Changes
The following code should no longer raise error:
```
export alias a = overlay use
```

# Tests + Formatting
Added 1 test.

# After Submitting
NaN

crates/nu-command/tests/commands/alias.rs

@@ -163,3 +163,9 @@ fn alias_default_help() {
     let first_help_line = actual.out.lines().next().unwrap();
     assert!(first_help_line.starts_with("Alias for `echo 'I am a beautiful teapot'`"));
 }
+
+#[test]
+fn export_alias_with_overlay_use_works() {
+    let actual = nu!("export alias teapot = overlay use");
+    assert!(actual.err.is_empty())
+}

crates/nu-parser/src/parse_keywords.rs

@@ -1147,6 +1147,7 @@ pub fn parse_export_in_block(
     }
 
     if let Some(decl_id) = working_set.find_decl(full_name.as_bytes()) {
+        let starting_error_count = working_set.parse_errors.len();
         let ParsedInternalCall { call, output, .. } = parse_internal_call(
             working_set,
             if full_name == "export" {
@@ -1161,12 +1162,12 @@ pub fn parse_export_in_block(
             },
             decl_id,
         );
+        // don't need errors generated by parse_internal_call
+        // further error will be generated by detail `parse_xxx` function.
+        working_set.parse_errors.truncate(starting_error_count);
 
         let decl = working_set.get_decl(decl_id);
-
-        let starting_error_count = working_set.parse_errors.len();
         check_call(working_set, call_span, &decl.signature(), &call);
-
         let Ok(is_help) = has_flag_const(working_set, &call, "help") else {
             return garbage_pipeline(working_set, &lite_command.parts);
         };