Fix last_content_without_template

[ziyi-curiousthing]

Fix last_content_without_template when the template looks like "Tell me a joke about {subject} with less than 50 words." where len(field_name_arr) < len(literal_text_arr). Existing implementation error out like the following:

Traceback (most recent call last):
  File "/Users/zz/src/GPTCache/sbert_match.py", line 62, in <module>
    response = openai.ChatCompletion.create(
  File "/Users/zz/src/GPTCache/gptcache/adapter/openai.py", line 125, in create
    return adapt(
  File "/Users/zz/src/GPTCache/gptcache/adapter/adapter.py", line 55, in adapt
    pre_embedding_res = time_cal(
  File "/Users/zz/src/GPTCache/gptcache/utils/time.py", line 9, in inner
    res = func(*args, **kwargs)
  File "/Users/zz/src/GPTCache/gptcache/processor/pre.py", line 134, in last_content_without_template
    pattern_value = _get_pattern_value(cache_config.template, last_content_str)
  File "/Users/zz/src/GPTCache/gptcache/processor/pre.py", line 72, in _get_pattern_value
    pattern_values[field_name_arr[i]] = value_str[start:end]
IndexError: list index out of range

[sre-ci-robot]

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[sre-ci-robot]

Welcome @ziyi-curiousthing! It looks like this is your first PR to zilliztech/GPTCache 🎉

[SimFG]

@ziyi-curiousthing thanks your contribution!

[ziyi-curiousthing]

@SimFG It looks like unittest is failing due to missing dependency. I am not sure how to fix it.

[SimFG]

@ziyi-curiousthing i will check it