refactor(cli): remove generic argument from notify<T>()

[rix0rrr]

The IIoHost interface has the following method:

interface IIoHost {
  notify<T>(msg: IoMessage<T>): Promise<void>;
}

The generic parameter T is only used once, without bounds, for a singleton argument in input position. This means it is equivalent to the following:

interface IIoHost {
  notify(msg: IoMessage<unknown>): Promise<void>;
}

(Preferring unknown over any so that implementors are forced to test for the type of the data field, just like they would need to do with an argument of type T)

In the words of the Java generics tutorial:

Generic methods allow type parameters to be used to express
dependencies among the types of one or more arguments to a method and/or
its return type. If there isn't such a dependency, a generic method
should not be used.

Or similar advice for TypeScript:

Type Parameters Should Appear Twice

Type parameters are for relating the types of multiple values. If a
type parameter is only used once in the function signature, it's not
relating anything.

---

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[codecov-commenter]

Codecov Report

Attention: Patch coverage is 85.71429% with 1 line in your changes missing coverage. Please review.

Project coverage is 85.08%. Comparing base (4566d8d) to head (1b7d105).
Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
packages/aws-cdk/lib/cli/activity-printer/base.ts	66.66%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #217      +/-   ##
==========================================
+ Coverage   85.02%   85.08%   +0.05%     
==========================================
  Files         208      208              
  Lines       35657    35657              
  Branches     4630     4621       -9     
==========================================
+ Hits        30318    30337      +19     
+ Misses       5181     5167      -14     
+ Partials      158      153       -5     

Flag	Coverage Δ
suite.unit	85.08% <85.71%> (+0.05%)	⬆️

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