Update azure-preview-portal-using-resource-groups.md

Fixed some typos - it looks like there is other text that could use some work, but I don't have time to fix them - sorry!
Cheers,
Jason Gerend - Writer, Windows Server (Jgerend)
Merge pull request #1880 from JasonGerend/patch-1

Update azure-preview-portal-using-resource-groups.md