chore(rc,profile,aliases,completion,libs,functions): Remove shebangs from sourced files

These files are always sourced (never executed directly), so the
#!/bin/bash shebang is inert and misleading. Drop it consistently
across rc.d/*, profile.d/*, and aliases.d/*.

completion.d/aws

@@ -1,5 +1,3 @@
-#!/bin/bash
-
 if (command -v aws && command -v aws_completer) &>/dev/null; then
   complete -C aws_completer aws
 fi