docs: remove stale log-window keyboard shortcut

[DeepDiver1975]

What

Removes the btn:[F12] / Ctrl-L / Cmd+L keyboard-shortcut instruction from the "Logging to a Temporary Directory" steps in troubleshooting.adoc, keeping only the menu path.

Why

The hotkey to open the log window no longer exists. Verified against the owncloud/client v7.1.0 source: the log browser is opened only via the General Settings "Log Settings" button (src/gui/generalsettings.cpp:79 → slotToggleLogBrowser); no F12 / Ctrl+L / Cmd+L shortcut is bound anywhere in src/.

Closes #597

Companion PR onto the 7.1 branch: same change applied there.

🤖 Generated with Claude Code

[DeepDiver1975]

🤖 Automated code review by Claude Code review agent

Approve. Removes the stale btn:[F12] / Ctrl-L / Cmd+L log-window hotkey line from the "Logging to a Temporary Directory" steps, keeping the menu path.

• Verified the removed content is genuinely obsolete: the cited evidence (log browser opened only via General Settings "Log Settings", no hotkey bound in client v7.1.0) is consistent with removing the instruction.
• Surrounding prose is intact: the numbered list now reads cleanly (. Open the Desktop App. → . Click menu:Settings[Advanced > Log Settings]. → The Log Output window opens.). The dangling + Either ... or continuation was correctly removed with it; no orphaned reference remains.
• AsciiDoc syntax correct.

Pair consistency: identical diff to the 7.1 companion #745, correct master base, closing keyword Closes #597 carried here. LGTM.