fix(vim.system): invalid MAX_TIMEOUT for 32-bit systems #31638

The maximum signed value on 32-bit systems is 2 ^ 31 - 1. When using 2 ^ 31 for
the default timeout, the value would overflow on such systems resulting in
a negative value, which caused a stack trace when calling wait() without
a timeout.

runtime/lua/vim/_system.lua

@@ -79,7 +79,8 @@ function SystemObj:_timeout(signal)
   self:kill(signal or SIG.TERM)
 end
 
-local MAX_TIMEOUT = 2 ^ 31
+-- Use max 32-bit signed int value to avoid overflow on 32-bit systems. #31633
+local MAX_TIMEOUT = 2 ^ 31 - 1
 
 --- @param timeout? integer
 --- @return vim.SystemCompleted