fix(windows): set manifest resource ID to 1 in nvim.rc for MinGW (#36611)

fix(windows): wrong RT_MANIFEST ID in nvim.rc #36406

Problem:
Starting Nvim on MinGW fails:
https://github.com/msys2/MINGW-packages/issues/25140

    Unknown system error -1："C:\msys64\ucrt64\bin\nvim.exe"Failed to start Nvim server!

Solution:
On Windows, the main application manifest should use resource ID 1 (RT_MANIFEST).
Update `nvim.rc` to use `1 RT_MANIFEST nvim.manifest` instead of `2`,
ensuring the manifest is correctly embedded and recognized by the system.

ID = 1 is for executable files (.exe)
ID = 2 is for DLLs (/DLL)
From MSVC docs: "Use a value of 2 for a DLL to enable it to specify private dependencies."
https://learn.microsoft.com/en-us/cpp/build/reference/manifest-create-side-by-side-assembly-manifest

(cherry picked from commit 2c04ae9fcc)

Co-authored-by: SquallATF <squallatf@gmail.com>

src/nvim/os/nvim.rc

@@ -1,2 +1,2 @@
 #include "winuser.h"
-2 RT_MANIFEST nvim.manifest
+1 RT_MANIFEST nvim.manifest