tar: Don't take -I to mean bzip2.

It hasn't meant bzip2 since GNU tar 1.13.18 (2000) and means something
different since 1.22 (2009).

completions/tar

@@ -33,7 +33,7 @@ _tar()
             fi
             return 0
             ;;
-        +([^IZzJjy])f)
+        +([^ZzJjy])f)
             ext="$tars"
             regex='\(\(tar\|gem\|spkg\)\(\.\(Z\|[gx]z\|bz2\?\|lzma\)\)\?\|t\([glx]z\|bz2\?\)\)'
             ;;
@@ -41,7 +41,7 @@ _tar()
             ext='@(t?(ar.)|gem.|spkg.)@(gz|Z)'
             regex='\(t\(ar\.\)\?\|gem\.\|spkg\.\)\(gz\|Z\)'
             ;;
-        *[Ijy]*f)
+        *[jy]*f)
             ext='@(@(t?(ar.)|gem.)bz?(2)|spkg)'
             regex='\(\(t\(ar\.\)\?\|gem\.\)bz2\?\|spkg\)'
             ;;
@@ -62,7 +62,7 @@ _tar()
             # get name of tar file from command line
             tar=$( sed -e 's/^.* \([^ ]*'$regex'\) .*$/\1/' <<<"${words[@]}" )
             # devise how to untar and list it
-            untar=t${words[1]//[^IJzjyf]/}
+            untar=t${words[1]//[^Jzjyf]/}
 
             local IFS=$'\n'
             COMPREPLY=( $( compgen -W "$( printf '%s\n' $( tar $untar $tar \