chore: xrootd-5.6.9

Updating the xrootd client to 5.6.9 to mitigate https://github.com/xrootd/xrootd/issues/2082. Uses https://github.com/spack/spack/commit/62132919e1465a40e3522e40278e4bbc8ec32978.

spack.sh

@@ -61,10 +61,6 @@ e8ae9a403ca7db7738d36bf41bf99977b9c88a84
 5a52780f7cf09973c431f89713db1c571ddd2ccc
 28d02dff6090b72e070c5b9497cd1f4372b4723f
 6008ae0c607560e4320dad5dcb35aaa4e1bc5d50
-27c8135207d27015181c3b093e5bd37146e801b1
-082afe04b84c201f84b4d9cf9bdc8e3e8dbdeb8f
-9259a6aae4d2280d4c7247f328aeba45186ac7c8
-9438cac219cc7ff127e03bc8a09dcb5d67124bb7
 19c20563cc86140aaf352d72079bd9de292be0ac
 62132919e1465a40e3522e40278e4bbc8ec32978
 ---