[SPARK-33479][DOC][FOLLOWUP] DocSearch: Support filtering search results by version
[SPARK-33479][DOC][FOLLOWUP] DocSearch: Support filtering search results by version

### What changes were proposed in this pull request?

In the discussion https://github.com/apache/spark/pull/30292#issuecomment-725613417, we planned to apply a new API key for each Spark release. However, it turns that DocSearch supports crawling multiple URLs from one website and filtering by fact key: https://docsearch.algolia.com/docs/config-file/#using-regular-expressions

Thanks to the help from shortcuts, our Spark doc supports multiple version now: https://github.com/algolia/docsearch-configs/pull/2868

This PR is to add the fact key in the search script and update the instruction in the comment.

### Why are the changes needed?

To support filtering Spark documentation search results by the current document version.

### Does this PR introduce _any_ user-facing change?

No

### How was this patch tested?

Manual test

Closes #30469 from gengliangwang/apiKeyFollowUp.

Authored-by: Gengliang Wang <bfe1a7b36425bd89859a70a36586361d28ec35eb@databricks.com>
Signed-off-by: Takeshi Yamamuro <9770f4f4b25a32d3dfa34670a10767defeb974f3@apache.org>

wangyum/spark,apache/spark,HyukjinKwon/spark,milliman/spark,cloud-fan/spark,holdenk/spark,xuanyuanking/spark,cloud-fan/spark,zzcclp/spark,mahak/spark,gengliangwang/spark,nchammas/spark,wangmiao1981/spark,taroplus/spark,taroplus/spark,hvanhovell/spark,milliman/spark,WeichenXu123/spark,holdenk/spark,ueshin/apache-spark,WeichenXu123/spark,chuckchen/spark,vinodkc/spark,srowen/spark,zzcclp/spark,shaneknapp/spark,dongjoon-hyun/spark,jiangxb1987/spark,jiangxb1987/spark,srowen/spark,zero323/spark,ueshin/apache-spark,milliman/spark,mahak/spark,maropu/spark,chuckchen/spark,srowen/spark,chuckchen/spark,chuckchen/spark,cloud-fan/spark,rednaxelafx/apache-spark,dongjoon-hyun/spark,rednaxelafx/apache-spark,milliman/spark,JoshRosen/spark,jiangxb1987/spark,WeichenXu123/spark,HyukjinKwon/spark,vinodkc/spark,cloud-fan/spark,WeichenXu123/spark,apache/spark,zzcclp/spark,jiangxb1987/spark,zzcclp/spark,wangmiao1981/spark,mahak/spark,gengliangwang/spark,maropu/spark,holdenk/spark,witgo/spark,dongjoon-hyun/spark,mahak/spark,hvanhovell/spark,taroplus/spark,mahak/spark,JoshRosen/spark,wangyum/spark,rednaxelafx/apache-spark,BryanCutler/spark,maropu/spark,taroplus/spark,xuanyuanking/spark,shaneknapp/spark,zero323/spark,apache/spark,wangyum/spark,jiangxb1987/spark,wangmiao1981/spark,rednaxelafx/apache-spark,taroplus/spark,gengliangwang/spark,apache/spark,zero323/spark,JoshRosen/spark,vinodkc/spark,WeichenXu123/spark,nchammas/spark,gengliangwang/spark,cloud-fan/spark,shaneknapp/spark,xuanyuanking/spark,holdenk/spark,witgo/spark,nchammas/spark,srowen/spark,milliman/spark,JoshRosen/spark,chuckchen/spark,shaneknapp/spark,nchammas/spark,apache/spark,BryanCutler/spark,jiangxb1987/spark,srowen/spark,maropu/spark,vinodkc/spark,holdenk/spark,apache/spark,zero323/spark,mahak/spark,witgo/spark,shaneknapp/spark,ueshin/apache-spark,jiangxb1987/spark,cloud-fan/spark,rednaxelafx/apache-spark,ueshin/apache-spark,wangyum/spark,srowen/spark,BryanCutler/spark,hvanhovell/spark,nchammas/spark,rednaxelafx/apache-spark,chuckchen/spark,milliman/spark,zzcclp/spark,wangmiao1981/spark,BryanCutler/spark,hvanhovell/spark,dongjoon-hyun/spark,HyukjinKwon/spark,hvanhovell/spark,maropu/spark,dongjoon-hyun/spark,witgo/spark,dongjoon-hyun/spark,holdenk/spark,gengliangwang/spark,srowen/spark,JoshRosen/spark,BryanCutler/spark,WeichenXu123/spark,dongjoon-hyun/spark,vinodkc/spark,ueshin/apache-spark,zero323/spark,maropu/spark,JoshRosen/spark,wangmiao1981/spark,vinodkc/spark,xuanyuanking/spark,wangyum/spark,wangyum/spark,shaneknapp/spark,taroplus/spark,mahak/spark,milliman/spark,holdenk/spark,witgo/spark,gengliangwang/spark,taroplus/spark,vinodkc/spark,witgo/spark,gengliangwang/spark,wangmiao1981/spark,xuanyuanking/spark,nchammas/spark,zzcclp/spark,hvanhovell/spark,apache/spark,JoshRosen/spark,BryanCutler/spark,BryanCutler/spark,wangyum/spark,maropu/spark,HyukjinKwon/spark,WeichenXu123/spark,ueshin/apache-spark,zero323/spark,shaneknapp/spark,xuanyuanking/spark,zzcclp/spark,ueshin/apache-spark,HyukjinKwon/spark,xuanyuanking/spark,HyukjinKwon/spark,nchammas/spark,zero323/spark,cloud-fan/spark,HyukjinKwon/spark,rednaxelafx/apache-spark,wangmiao1981/spark,witgo/spark,hvanhovell/spark,chuckchen/spark