fix(tar): do not associate with *.gem.<compress-extension>

To my knowledge, gems are just `*.gem`, not e.g. `*.gem.xz` etc.

Author: scop

completions/tar

@@ -441,7 +441,7 @@ __tar_cleanup_prev()
 
 __tar_detect_ext()
 {
-    local tars='@(@(tar|gem|spkg)?(.@(Z|[bgx]z|bz2|lz?(ma|o)|zst))|t@([abglx]z|b?(z)2|zst)|cbt|xbps)'
+    local tars='@(@(tar|spkg)?(.@(Z|[bgx]z|bz2|lz?(ma|o)|zst))|t@([abglx]z|b?(z)2|zst)|cbt|gem|xbps)'
     if [[ ${COMP_WORDS[0]} == ?(*/)bsdtar ]]; then
         # https://github.com/libarchive/libarchive/wiki/LibarchiveFormats
         tars=${tars/%\)/|pax|cpio|iso|zip|@(j|x)ar|mtree|a|7z|warc}
@@ -473,13 +473,13 @@ __tar_detect_ext()
             # Pass through using defaults above
             ;;
         *[Zz]*f)
-            ext='@(@(t?(ar.)|gem.|spkg.)@(gz|Z)|taz)'
+            ext='@(@(t?(ar.)|spkg.)@(gz|Z)|taz)'
             ;;
         *[jy]*f)
-            ext='@(@(t?(ar.)|gem.)bz?(2)|spkg|tb2)'
+            ext='@(t?(ar.)bz?(2)|spkg|tb2)'
             ;;
         *[J]*f)
-            ext='@(@(tar|gem|spkg).@(lzma|xz)|t[lx]z)'
+            ext='@(@(tar|spkg).@(lzma|xz)|t[lx]z)'
             ;;
     esac
 }