Add 2.5 support on bin/update aswell

[inductor]

Issue #, if available:
When executing bin/update on Ubuntu 18.04 the following error occurs

I, [2018-11-18T12:52:17.107054 #5065]  INFO -- : Starting Ruby version check.
E, [2018-11-18T12:52:17.107206 #5065] ERROR -- : Unhandled exception: #<TypeError: no implicit conversion of nil into String>
E, [2018-11-18T12:52:17.107241 #5065] ERROR -- :   at /opt/codedeploy-agent/bin/update:128:in `+'
E, [2018-11-18T12:52:17.107259 #5065] ERROR -- :   at /opt/codedeploy-agent/bin/update:128:in `unsupported_ruby_version_error'
E, [2018-11-18T12:52:17.107275 #5065] ERROR -- :   at /opt/codedeploy-agent/bin/update:123:in `check_ruby_version_and_symlink'
E, [2018-11-18T12:52:17.107300 #5065] ERROR -- :   at /opt/codedeploy-agent/bin/update:260:in `<main>'

Description of changes:

Add 2.5 in the array for workaround

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[coveralls]

Coverage decreased (-0.06%) to 92.009% when pulling 593031c on inductor:master into dc22129 on aws:master.

[rohkat-aws]

@inductor thanks for the pull request. Will be merging it soon

[inductor]

@rohkat-aws any updates?

[inductor]

@rohkat-aws

[fusion27]

Experiencing the same in Ubuntu 18.04. Is this PR the fix?

[inductor]

@rohkat-aws Please

[fusion27]

@inductor Have you tried downgrading Ruby? Looks like 2.4 support is there!

[inductor]

@fusion27 This is not an Issue... It's a PR lol

[fusion27]

@inductor ... which you've been waiting on since Nov 19th of last year. I gotta keep moving in my work and don't have the luxury of waiting for this PR to be merged. Will try downgrading when I get home tonight and am able to return to my studies.

[inductor]

@fusion27

Of course I haven’t been just sitting around here... and you should understand that's not the point here.

[inductor]

@rohkat-aws ping 😓

[hdm]

ruby 2.6.0 shipped, this could use an update

[inductor]

Well, this has been ignored for ages anyway 😂

[Helen1987]

Close the PR since the change has been already added in a different commit