Fixing memory available options for aws batch: 4 cpus

[kikemolina3]

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When I try to select a aws batch runtime with 4 CPUs and 30GB memory (fargate container), I get this exception:

2026-01-21 13:10:46,494 [INFO] config.py:139 -- Lithops v3.6.3.dev0 - Python3.10
Traceback (most recent call last):
  File "/home/manri-urv/urv/serverlens/microbench/run_experiments.py", line 66, in <module>
    full_experiments()
  File "/home/manri-urv/urv/serverlens/microbench/run_experiments.py", line 62, in full_experiments
    benchmark(backend, cpu, size_overhead, memory)
  File "/home/manri-urv/urv/serverlens/microbench/cli.py", line 45, in benchmark
    fexec = lithops.FunctionExecutor(backend=backend, **kwargs)
  File "/home/manri-urv/urv/serverlens/.venv/lib/python3.10/site-packages/lithops/executors.py", line 107, in __init__
    self.config = default_config(config_file=config_file, config_data=config, config_overwrite=config_ow)
  File "/home/manri-urv/urv/serverlens/.venv/lib/python3.10/site-packages/lithops/config.py", line 181, in default_config
    cb_config.load_config(config_data)
  File "/home/manri-urv/urv/serverlens/.venv/lib/python3.10/site-packages/lithops/serverless/backends/aws_batch/config.py", line 123, in load_config
    raise Exception(
Exception: '30720' runtime memory is not valid for 4 vCPU and the FARGATE environment (for 4vCPU choose one of 8192, 9216, 10240, 11264, 12288, 13312, 14336, 15360, 16384, 17408, 18432, 19456, 20480, 21504, 22528, 23552, 24576, 25600, 26624, 27648, 28672)

This PR fixes this problem, increasing the options for 4 CPUs in fargate until 30GB (included)

[JosepSampe]

Thanks!