[Fix] `nvm_get_default_packages`: use `awk` for more reliable file pr… #1308

Job	Run time
shellcheck_matrix (bash, nvm.sh)	40s
shellcheck_matrix (sh, nvm.sh)	38s
shellcheck_matrix (dash, nvm.sh)	39s
shellcheck_matrix (ksh, nvm.sh)	47s
shellcheck_matrix (bash, install.sh)	21s
shellcheck_matrix (bash, bash_completion)	17s
shellcheck_matrix (bash, nvm-exec)	30s
shellcheck	1s
	3m 53s

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