Disabling AGC debugging option

I am wondering if it is already the right time to disable by default the AGC debugging option under DEBUG_AGC_ENCODER_CMD_OPTION.

The motivation is

1. to have the framework closer to the final delivery
2. address the following todo comment in ivas_spar_enc_process() which will change the bitstream:

/* IVAS_fmToDo: This AGC on/off bit should be removed when the command line option to force enable/disable AGC is
 * removed.
 * On the decoder side, ivas_agc_enc_get_flag could be used instead to determine if AGC is on or not. The
 * ivas_agc_enc_get_flag function should be moved to ivas_agc_com.c and renamed when this occurs. */
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