[Android] Set ANDROID_HOME instead of deprecated ANDROID_SDK_ROOT

[mosabab]

Platforms affected

Android

Motivation and Context

Closes #1296

ANDROID_HOME is default
Since this PR: apache/cordova-android#1471
The documentation should be deal with latest updates.
Because ANDROID_HOME is new default and ANDROID_SDK_ROOT is deprecated.

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Also to insure that Android SDK Command-line Tools is selected.

Description

Testing

Checklist

• I've run the tests to see all new and existing tests pass
• I added automated test coverage as appropriate for this change
• Commit is prefixed with (platform) if this change only applies to one platform (e.g. (android))
• If this Pull Request resolves an issue, I linked to the issue in the text above (and used the correct keyword to close issues using keywords)
• I've updated the documentation if necessary

[mosabab]

@breautek Thanks for explain.

[breautek]

Looks good to me, will merge in 48 hours unless someone else have further comments.