upip: Update utarfile from upstream.

upip/upip_utarfile.py

@@ -12,12 +12,6 @@ REGTYPE = "file"
 def roundup(val, align):
     return (val + align - 1) & ~(align - 1)
 
-def skip(f, size):
-    assert size % 512 == 0
-    buf = bytearray(512)
-    while size:
-        size -= f.readinto(buf)
-
 class FileSection:
 
     def __init__(self, f, content_len, aligned_len):