Make fastapi install optional and relax pinning from `setup.py` requirements

[jmahlik]

Describe the bug
68ff700#diff-60f61ab7a8d1910d86d9fda2261620314edcae5894d5aaa236b821c7256badd7R67-R72 introduced pinned dependencies in the setup.py.

These will inevitably conflict with downstream users ability to install sagemaker alongside fastapi or uvcorn. Relax the restrictions on the deps.

** edit **
On second thought, why are fastapi and uvicorn listed as dependencies? I don't see any references to them in the codebase on the current master/v2.203.0. These should either be removed or set as optional extra installs.

Not imported anywhere? Only shows in the setup.py.

git grep --ignore-case -e 'fastapi'
setup.py:    "fastapi==0.95.2",

Using pipdeptree shows these packages bring in other transitive deps which increases the install load if they aren't used or only used for a niche feature.

pipdeptree  -p fastapi,uvicorn
fastapi==0.95.2
├── pydantic [required: >=1.6.2,<2.0.0,!=1.8.1,!=1.8,!=1.7.3,!=1.7.2,!=1.7.1,!=1.7, installed: 1.10.13]
│   └── typing-extensions [required: >=4.2.0, installed: 4.9.0]
└── starlette [required: >=0.27.0,<0.28.0, installed: 0.27.0]
    └── anyio [required: >=3.4.0,<5, installed: 4.2.0]
        ├── idna [required: >=2.8, installed: 3.6]
        └── sniffio [required: >=1.1, installed: 1.3.0]
uvicorn==0.22.0
├── click [required: >=7.0, installed: 8.1.7]
│   └── colorama [required: Any, installed: 0.4.6]
└── h11 [required: >=0.8, installed: 0.14.0]

To reproduce
This was introduced in release 2.199.0.

python -m pip install sagemaker==2.203.0 results in unresolvable deps if fastapi is pinned in a users requirements.

Expected behavior
Install to resolve without restricting the version of fastapi.

Screenshots or logs
If applicable, add screenshots or logs to help explain your problem.

System information
A description of your system. Please provide:

• SageMaker Python SDK version: 2.203.0
• Framework name (eg. PyTorch) or algorithm (eg. KMeans): n/a
• Framework version: n/a
• Python version: 3.12/3.11/3.10/3.9
• CPU or GPU: cpu
• Custom Docker image (Y/N): N

Additional context
Add any other context about the problem here.

[jmahlik]

Also releated: #4295

[j-adamczyk]

+1. Why is this even included if it's not used?