take out deprecated extrinsic

[ETeissonniere]

As of today, we use the new batch extrinsic for allocations, not allocate
anymore, so we can take it out.

[codecov]

Codecov Report

Merging #648 (1403ba4) into master (d0c20b0) will decrease coverage by 0.08%.
The diff coverage is 55.26%.

@@            Coverage Diff             @@
##           master     #648      +/-   ##
==========================================
- Coverage   89.73%   89.64%   -0.09%     
==========================================
  Files          33       33              
  Lines        6232     6169      -63     
==========================================
- Hits         5592     5530      -62     
+ Misses        640      639       -1     

Impacted Files	Coverage Δ
node/src/chain_spec.rs	0.00% <ø> (ø)
node/src/cli.rs	0.00% <0.00%> (ø)
node/src/rpc.rs	0.00% <0.00%> (ø)
node/src/service.rs	0.00% <0.00%> (ø)
pallets/grants/src/benchmarking.rs	100.00% <ø> (ø)
pallets/grants/src/lib.rs	62.96% <ø> (ø)
runtimes/eden/src/pallets_parachain.rs	0.00% <ø> (ø)
runtimes/eden/src/pallets_system.rs	0.00% <ø> (ø)
runtimes/eden/src/pallets_util.rs	0.00% <ø> (ø)
runtimes/eden/src/version.rs	0.00% <ø> (ø)
... and 9 more

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