Remove `micromatch` from package.json

[jsoref]

• When Swap the jest testing framwork for ava #18 landed, it included:
  

  codeql-action/package.json

  Line 44 in d7b9f5a

  "ava": "3.8.1",

  
  

  codeql-action/package.json

  Lines 36 to 38 in d7b9f5a

  	"//": [
  	"micromatch is an unspecified dependency of ava"
  	],

• That dependency was fixed in avajs/ava@fd92b4a which was released in https://github.com/avajs/ava/releases/tag/v3.8.2
• ava was upgraded a while ago to pull in that fix:

  codeql-action/package.json

  Line 64 in 531c6ba

  "ava": "^3.15.0",