Remove outdated CVEs from .nancy-ignore (#1791)

Author: Sergey Vilgelm

.nancy-ignore

@@ -1,10 +1,3 @@
-# Skip for golang/golang.org/x/[email protected]
-CVE-2018-17848
-CVE-2018-17143
-CVE-2018-17847
-CVE-2018-17142
-CVE-2018-17846
-
 # Skip for indirect dependency github.com/coreos/[email protected]
 CVE-2020-15114
 CVE-2020-15115