luci-mod-network: fix uci.remove() deleting entire radio section on wifi join

[weicheng04]

Problem

When joining a Wi-Fi network via Scan → Join Network, if the scanned BSS
has no VHT/HE capability information (e.g. a basic 802.11b/g/n AP), the
handleJoinConfirm callback enters the else branch at line 2152 and calls:

uci.remove('wireless', radioDev.getName(), 'htmode');

The intent is to remove only the htmode option. However, uci.remove()
in uci.js only accepts two parameters (conf, sid) — the third parameter
is silently ignored. This causes the entire wifi-device section (e.g.
radio0) to be marked for deletion in the rpcd session delta.

Symptoms

• After clicking "Join Network", the Wireless Overview page shows
  "This section contains no values yet"
• All wifi-iface entries disappear from the page
• The rpcd session delta file contains -wireless.radio0
• The bug persists until the user logs out or the session expires

Root Cause

uci.js defines:

• remove(conf, sid) → deletes entire section
• unset(conf, sid, opt) → removes a single option (calls set(conf, sid, opt, null))

The code should use uci.unset() instead of uci.remove() when removing
a single option.

Fix

-				uci.remove('wireless', radioDev.getName(), 'htmode');
+				uci.unset('wireless', radioDev.getName(), 'htmode');

Testing

Tested on OpenWrt 24.10-SNAPSHOT (aarch64, BCM43455):

1. Network → Wireless → Scan → Join a 2.4GHz b/g/n network
2. Wireless Overview page displays correctly after join
3. uci show wireless confirms radio0 section is preserved

[systemcrash]

Merged. Thanks @weicheng04

[github-actions]

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Commit c1bbb05

• 🔶 Author name must be either a real name 'firstname lastname' or a nickname/alias/handle
  Actual: weicheng04 seems to be a nickname or an alias
  Expected: a real name 'firstname lastname'
• 🔶 Commit(ter) name must be either a real name 'firstname lastname' or a nickname/alias/handle
  Actual: weicheng04 seems to be a nickname or an alias
  Expected: a real name 'firstname lastname'
• 🔶 Commit subject must be <= 80 (and should be <= 60) characters long
  Actual: subject is 77 characters long
  $\textsf{luci-mod-network: fix uci.remove() deleting entire radio sec\color{yellow}{tion on wifi join}\color{red}{}}$
• ❌ Signed-off-by must match author
  Actual: missing or doesn't match author
  Expected: Signed-off-by: weicheng04 <weicheng.xiao@outlook.com>

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