examples : update args speculative-simple README.md [no ci] (#22938)

examples : update args speculative-simple README.md [no ci] (#22938)

This commit updates the command line arguments to use the correct names
and values which are now required.

The motivation for this change is that currently running the example
command as is will generate the following errors:
```console
error while handling argument "--color": error: unknown value for --color: '--sampling-seq'

usage:
-co,   --color [on|off|auto]            Colorize output to distinguish prompt and user input from generations
                                        ('on', 'off', or 'auto', default: 'auto')
                                        'auto' enables colors when output is to a terminal

error while handling argument "-fa": error: unknown value for --flash-attn: '--temp'

usage:
-fa,   --flash-attn [on|off|auto]       set Flash Attention use ('on', 'off', or 'auto', default: 'auto')
                                        (env: LLAMA_ARG_FLASH_ATTN)

error while handling argument "--draft-max": the argument has been removed. use --spec-draft-n-max or --spec-ngram-mod-n-max

usage:
--draft, --draft-n, --draft-max N       the argument has been removed. use --spec-draft-n-max or
                                        --spec-ngram-mod-n-max
                                        (env: LLAMA_ARG_DRAFT_MAX)

error while handling argument "--draft-min": the argument has been removed. use --spec-draft-n-min or --spec-ngram-mod-n-min

usage:
--draft-min, --draft-n-min N            the argument has been removed. use --spec-draft-n-min or
                                        --spec-ngram-mod-n-min
                                        (env: LLAMA_ARG_DRAFT_MIN)
```