Mark some function arguments as [consumed] in the docs.

The argument argv of job_start() and channel_from_job() will be
freed. Mark them as such in the comments of this functions.

src/nvim/msgpack_rpc/channel.c

@@ -119,7 +119,7 @@ void channel_teardown(void)
 /// Creates an API channel by starting a job and connecting to its
 /// stdin/stdout. stderr is forwarded to the editor error stream.
 ///
-/// @param argv The argument vector for the process
+/// @param argv The argument vector for the process. [consumed]
 /// @return The channel id
 uint64_t channel_from_job(char **argv)
 {

src/nvim/os/job.c

@@ -106,6 +106,7 @@ void job_teardown(void)
 ///
 /// @param argv Argument vector for the process. The first item is the
 ///             executable to run.
+///             [consumed]
 /// @param data Caller data that will be associated with the job
 /// @param writable If true the job stdin will be available for writing with
 ///                 job_write, otherwise it will be redirected to /dev/null