Fix linting errors in crosslinking_issues.md

Fix linting errors in https://docs.gitlab.com/ee/user/project/issues/crosslinking_issues.html

Related: #284446 (closed)

35:44  error  Avoid using future tense: "going to be". Use present tense instead.   gitlab.FutureTense
37:4   error  Avoid using future tense: "will measure". Use present tense instead.  gitlab.FutureTense
48:60  error  Avoid using future tense: "will also". Use present tense instead.     gitlab.FutureTense
59:62  error  Avoid using future tense: "will simply". Use present tense instead.   gitlab.FutureTense

If you'd like to work on this issue, mention @msedlakjakubowski in a comment. Then, in your merge request's description, paste this issue's URL so they become linked.