Fix shebang in check_components script

[grieshaber]

Tiny PR, that fixes #113.

[comment-bot-dev]

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• ⚠️check_shell Failed shell check. More info on running shellcheck locally here.

  Running shellcheck
  In ./scripts/check_components.sh line 31:
  IFS=',' read -r -a CURRENTLY_INSTALLED <<< "$CURRENTLY_INSTALLED"
              ^-- SC2039: In POSIX sh, read -a is undefined.
                                     ^-^ SC2039: In POSIX sh, here-strings are undefined.
  In ./scripts/check_components.sh line 32:
  IFS=',' read -r -a PROPOSED_COMPONENTS_TO_INSTALL <<< "$PROPOSED_COMPONENTS_TO_INSTALL"
              ^-- SC2039: In POSIX sh, read -a is undefined.
                                                ^-^ SC2039: In POSIX sh, here-strings are undefined.
  In ./scripts/check_components.sh line 35:
  FILTER_COMPONENT_LIST=()
                    ^-- SC2039: In POSIX sh, arrays are undefined.
  In ./scripts/check_components.sh line 36:
  for component in "${PROPOSED_COMPONENTS_TO_INSTALL[@]}"
                ^-- SC2039: In POSIX sh, array references are undefined.
  In ./scripts/check_components.sh line 38:
  if [[ ! ${CURRENTLY_INSTALLED[*]} =~ $component ]]; then
     ^-- SC2039: In POSIX sh, [[ ]] is undefined.
          ^-----------------------^ SC2039: In POSIX sh, array references are undefined.
  In ./scripts/check_components.sh line 39:
      FILTER_COMPONENT_LIST+=("$component")
      ^-------------------^ SC2039: In POSIX sh, += is undefined.
                             ^------------^ SC2039: In POSIX sh, arrays are undefined.
  In ./scripts/check_components.sh line 46:
  FINAL_COMPONENT_LIST=()
                   ^-- SC2039: In POSIX sh, arrays are undefined.
  In ./scripts/check_components.sh line 47:
  for component in "${FILTER_COMPONENT_LIST[@]}"
                ^-------------------------^ SC2039: In POSIX sh, array references are undefined.
  In ./scripts/check_components.sh line 49:
  if [[ $(command -v "$component") ]]; then
     ^-- SC2039: In POSIX sh, [[ ]] is undefined.
  In ./scripts/check_components.sh line 52:
      FINAL_COMPONENT_LIST+=("$component")
      ^------------------^ SC2039: In POSIX sh, += is undefined.
                            ^------------^ SC2039: In POSIX sh, arrays are undefined.
  In ./scripts/check_components.sh line 58:
  if [[ ${FINAL_COMPONENT_LIST[*]} ]]; then
  ^-- SC2039: In POSIX sh, [[ ]] is undefined.
    ^------------------------^ SC2039: In POSIX sh, array references are undefined.
  In ./scripts/check_components.sh line 59:
  echo "Installing components ${FINAL_COMPONENT_LIST[*]}";
                              ^------------------------^ SC2039: In POSIX sh, array references are undefined.
  In ./scripts/check_components.sh line 60:
  $GCLOUD_PATH components install "${FINAL_COMPONENT_LIST[@]}" --quiet
                                   ^------------------------^ SC2039: In POSIX sh, array references are undefined.
  In ./scripts/check_components.sh line 62:
  echo "All components ${PROPOSED_COMPONENTS_TO_INSTALL[*]} already installed."
                       ^-- SC2039: In POSIX sh, array references are undefined.
  For more information:
  https://www.shellcheck.net/wiki/SC2039 -- In POSIX sh, += is undefined.

[grieshaber]

Closed this, b/c the fix isn't that tiny as i thought. I'll think about a different solution and create a new PR then.