[MINOR][DOC] Fix ml-guide markdown typos

[chucheng92]

What changes were proposed in this pull request?

Easy fix in the markdown.

How was this patch tested?

Tested manually

Please review http://spark.apache.org/contributing.html before opening a pull request.

[AmplabJenkins]

Can one of the admins verify this patch?

[felixcheung]

can you check if we have other typo in the md file?
or similar type of typo in other md files?

[chucheng92]

@felixcheung Yes, I read the entire docs of Spark Mlib. There is no problem with other mds (I may not have seen it or other contributors solved it). This error is obvious, and it affects the link of the later issue, so i found it.
http://spark.apache.org/docs/latest/ml-guide.html#breaking-changes

[chucheng92]

@felixcheung hi，In my reading process，I found another md file typos and fix it. Do I need to close this pr and merge it into one commit and give a new pr? Thanks.

[HyukjinKwon]

I think you can add all other typos into here.

[chucheng92]

@HyukjinKwon Thanks a lot, could u help me to review these commits if u have time。

[chucheng92]

can someone help me to close this pr? i have merged these commits to a new pr.
#20897

[felixcheung]

@lemonjing you need to close the PR from github.com - we don't have access to close it

[chucheng92]

@felixcheung thanks a lot. and i closed it.