Fix spurious clear-to-end sequence in buffer dumps (#17374)

I think I forgot to complete that section of the code...
The parentheses were missing and `beg` was repeated twice. The last
line in the comment above this explains what I intended it to be.

Closes #17365

## Validation Steps Performed
* In a new PowerShell tab
* Run ``"`e[999C`e[2D`e[42mfoo`e[m"``
* Newline until it scrolls
* Run it again
* Close and reopen
* The green "foo" is still green ✅

(cherry picked from commit 640424e)
Service-Card-Id: 92687334
Service-Version: 1.21

src/buffer/out/textBuffer.cpp

@@ -2789,7 +2789,7 @@ void TextBuffer::Serialize(const wchar_t* destination) const
             // In other words, we can only skip \x1b[K = Erase in Line, if both the first/last attribute are the default attribute.
             static constexpr TextAttribute defaultAttr;
             const auto trimTrailingWhitespaces = it == last && lastCharX < newX;
-            const auto clearToEndOfLine = trimTrailingWhitespaces && beg->value != defaultAttr || beg->value != defaultAttr;
+            const auto clearToEndOfLine = trimTrailingWhitespaces && (beg->value != defaultAttr || last->value != defaultAttr);
 
             if (trimTrailingWhitespaces)
             {