[Fix] `nvm_get_default_packages`: use `awk` for more reliable file pr… #1310

Job	Run time
shellcheck_matrix (bash, nvm.sh)	33s
shellcheck_matrix (sh, nvm.sh)	34s
shellcheck_matrix (dash, nvm.sh)	38s
shellcheck_matrix (ksh, nvm.sh)	44s
shellcheck_matrix (bash, install.sh)	28s
shellcheck_matrix (bash, bash_completion)	26s
shellcheck_matrix (bash, nvm-exec)	24s
shellcheck	1s
	3m 48s

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