Soften ReadScriptLogLineAsync comment to match root cause

The earlier comment asserted the EOF tight-loop was the cause of the
multi-hour Windows hang. Deconfounding analysis disproved that: the hang
is the in-box Windows PowerShell attach regression from the 20260614
runner image, not thread-pool starvation here. Keep the yield as genuine
harness hardening but describe it as such rather than claiming it as the
fix.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: andyleejordan

test/PowerShellEditorServices.Test.E2E/DebugAdapterProtocolMessageTests.cs

@@ -239,13 +239,11 @@ private async Task<string> ReadScriptLogLineAsync()
             }
 
             // Tail the log until a non-empty line is available. The awaited
-            // delay between reads is essential: at EOF ReadLineAsync completes
-            // synchronously with null, so without it this becomes a tight loop
-            // that never releases its thread-pool thread. On constrained CI
-            // runners that starves the pool, wedging the DAP client's
-            // background I/O (and the whole test) and defeating both the xUnit
-            // and harness timeouts so a stall hangs for hours instead of
-            // failing fast.
+            // delay between reads matters: at EOF ReadLineAsync completes
+            // synchronously with null, so without it this is a tight loop that
+            // never releases its thread-pool thread and needlessly pressures
+            // the pool on constrained CI runners. Yielding keeps the tail loop
+            // cheap while we wait for the script to write.
             while (true)
             {
                 string nextLine = await scriptLogReader.ReadLineAsync();