cmake: stop disabling C4774 after replacing snprintf(), update comment (MSVC)

- update comment for `-wd4710` option.
  Ref: https://ci.appveyor.com/project/curlorg/curl/builds/53627545
- stop suppressing C4774. Not triggered by the replacement call
  `vsnprintf()`, as also confirmed by local tests.
  Follow-up to 192b9214a7
  Ref: https://devblogs.microsoft.com/cppblog/format-specifiers-checking/
  Ref: https://learn.microsoft.com/cpp/error-messages/compiler-warnings/compiler-warnings-c4600-through-c4799

Follow-up to 64f28b8f88 #20765

Closes #20792

CMake/PickyWarnings.cmake

@@ -406,12 +406,11 @@ if(PICKY_COMPILER)
     list(APPEND _picky "-wd4548")  # expression before comma has no effect; expected expression with side-effect (in FD_SET())
     list(APPEND _picky "-wd4574")  # 'M' is defined to be '0': did you mean to use '#if M'? (in ws2tcpip.h)
     list(APPEND _picky "-wd4668")  # 'M' is not defined as a preprocessor macro, replacing with '0' for '#if/#elif' (in winbase.h)
-    list(APPEND _picky "-wd4710")  # 'snprintf': function not inlined
+    list(APPEND _picky "-wd4710")  # 'fprintf'/'printf'/'sscanf': function not inlined (in tests, with VS2022+ Release)
     list(APPEND _picky "-wd4711")  # function 'A' selected for automatic inline expansion
     # volatile access of '<expression>' is subject to /volatile:<iso|ms> setting;
     #   consider using __iso_volatile_load/store intrinsic functions (ARM64)
     list(APPEND _picky "-wd4746")
-    list(APPEND _picky "-wd4774")  # 'snprintf': format string expected in argument 3 is not a string literal
     list(APPEND _picky "-wd4820")  # 'A': 'N' bytes padding added after data member 'B'
     if(MSVC_VERSION GREATER_EQUAL 1900)
       list(APPEND _picky "-wd5045")  # Compiler will insert Spectre mitigation for memory load if /Qspectre switch specified