fix: remove unsupported parameter from initialization & update readme installation instructions

[matthewgoodman13]

Summary

Customers are unable to install the ECS MCP Server using uvx. When configuring the ECS MCP Server and starting it, they get the following error:

Traceback (most recent call last):
  File "/Users/asdf/.cache/uv/archive-v0/fM-nIq6nkiZfB0W5xjMll/bin/ecs-mcp-server", line 6, in <module>
    from awslabs.ecs_mcp_server.main import main
  File "/Users/asdf/.cache/uv/archive-v0/fM-nIq6nkiZfB0W5xjMll/lib/python3.13/site-packages/awslabs/ecs_mcp_server/main.py", line 72, in <module>
    mcp = FastMCP(
        name="AWS ECS MCP Server",
    ...<29 lines>...
    """,
    )
TypeError: FastMCP.__init__() got an unexpected keyword argument 'description'

This is related to a non-backwards compatible change that is being tracked here.

Changes

• remove the unsupported parameters
• update readme instructions with pre-reqs

User experience

• customers can install the ecs mcp server again successfully

Checklist

If your change doesn't seem to apply, please leave them unchecked.

• [Y] I have reviewed the contributing guidelines
• [Y] I have performed a self-review of this change
• [Y] Changes have been tested
• [Y] Changes are documented

Is this a breaking change? (Y/N) No.

RFC issue number:

Checklist:

• [NA] Migration process documented
• [NA] Implement warnings (if it can live side by side)

Acknowledgment

By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of the project license.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 89.12%. Comparing base (ab9bb07) to head (3e0d209).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #994      +/-   ##
==========================================
+ Coverage   88.72%   89.12%   +0.39%     
==========================================
  Files         574      527      -47     
  Lines       39156    35420    -3736     
  Branches     6019     5410     -609     
==========================================
- Hits        34743    31568    -3175     
+ Misses       2912     2550     -362     
+ Partials     1501     1302     -199     

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