bad CPU type in executable: wsk (macOS 10.15 Catalina)

## Description

This issue is purely informational (for search engines). macOS 10.15 Catalina can only run 64-bit apps. When downloading an executable from the Releases page, a user may be confused if they only have an Intel CPU, that they may not install the amd64 bit version, and use the 386 version instead. Suggest rename to `amd64` to `x86_64` in any zip filenames under the Releases tab.

## Expected
When I type `wsk` in the terminal, it runs

## Actual
When I type `wsk` in the terminal, it shows the error message `bad CPU type in executable: wsk`

## Steps to reproduce:
1. Install macOS 10.15 Catalina (Intel CPU)
2. Download the `OpenWhisk_CLI-latest-mac-386.zip` file from
https://github.com/apache/incubator-openwhisk-cli/releases/tag/latest
3. Unzip the file
4. Run `wsk`

## Workaround
Download the `OpenWhisk_CLI-latest-mac-amd64.zip` bundle instead, and run the `wsk` executable in there

# Suggested Fix
1. Rename `OpenWhisk_CLI-latest-mac-amd64.zip` to `OpenWhisk_CLI-latest-mac-x86_64.zip`