Macro: Unsupported symbols error message is incorrect

**Steps to Reproduce**

1. Switch to Macro - Sequence mode
2. Copy to clipboard following text - `BBBBB*****;;;;`
3. Start new sequence (via context menu)
4. Paste text from clipboard on the canvas

**Actual behavior**
System shows error message: `Pasted format could not be recognized.`
Also, please see additional example in the Comment.

**Expected behavior**
System should display Error message `Ketcher doesn't support symbols ... . Paste operation failed` and not to perform paste.

A per requirement https://github.com/epam/ketcher/issues/3894 - p.6:

> If unsupported symbols are entered during paste from clipboard then the system should display Error message "Ketcher doesn't support symbols ... . Paste operation failed" and not to perform paste.

**Versions:**
Windows 10
Chrome Version Version 123.0.6312.106 (Official Build) (64-bit)
Ketcher Version 2.21.0-rc.1 Build at 2024-04-15; 20:00:15
Indigo Toolkit Version 1.20.0-rc.1.0-g8e8ffc3c3-wasm32-wasm-clang-12.0.0

Issue found while testing https://github.com/epam/ketcher/issues/3894

Start by reproducing the Macro - Sequence paste steps with `BBBBB*****;;;;` and compare the current error with the requirement in Ketcher issue 3894, paragraph 6. Trace the Indigo Toolkit paste or unsupported-symbol handling path; done means unsupported symbols produce the specified error and the paste does not occur.

Written by the indexing model from the issue text.