contrib: move user32.dll from bitcoind.exe libs

The user interface library is no-longer needed by `bitcoind.exe`,
or utils, only `bitcoin-qt.exe`.
Add missing lib doc.

contrib/devtools/symbol-check.py

@@ -157,21 +157,21 @@ PE_ALLOWED_LIBRARIES = {
 'KERNEL32.dll', # win32 base APIs
 'msvcrt.dll', # C standard library for MSVC
 'SHELL32.dll', # shell API
-'USER32.dll', # user interface
 'WS2_32.dll', # sockets
 # bitcoin-qt only
 'dwmapi.dll', # desktop window manager
 'GDI32.dll', # graphics device interface
 'IMM32.dll', # input method editor
-'NETAPI32.dll',
+'NETAPI32.dll', # network management
 'ole32.dll', # component object model
 'OLEAUT32.dll', # OLE Automation API
 'SHLWAPI.dll', # light weight shell API
-'USERENV.dll',
-'UxTheme.dll',
+'USER32.dll', # user interface
+'USERENV.dll', # user management
+'UxTheme.dll', # visual style
 'VERSION.dll', # version checking
 'WINMM.dll', # WinMM audio API
-'WTSAPI32.dll',
+'WTSAPI32.dll', # Remote Desktop
 }
 
 def check_version(max_versions, version, arch) -> bool: