Remove Python 3.8 from README (pytorch#139089)

Pull Request resolved: pytorch#139089
Approved by: https://github.com/clee2000, https://github.com/malfet

Author: kit1980

README.md

@@ -160,7 +160,7 @@ They require JetPack 4.2 and above, and [@dusty-nv](https://github.com/dusty-nv)
 
 #### Prerequisites
 If you are installing from source, you will need:
-- Python 3.8 or later (for Linux, Python 3.8.1+ is needed)
+- Python 3.9 or later
 - A compiler that fully supports C++17, such as clang or gcc (gcc 9.4.0 or newer is required, on Linux)
 - Visual Studio or Visual Studio Build Tool on Windows
 
@@ -295,16 +295,6 @@ export CMAKE_PREFIX_PATH="${CONDA_PREFIX:-'$(dirname $(which conda))/../'}:${CMA
 python setup.py develop
 ```
 
-> _Aside:_ If you are using [Anaconda](https://www.anaconda.com/distribution/#download-section), you may experience an error caused by the linker:
->
-> ```plaintext
-> build/temp.linux-x86_64-3.7/torch/csrc/stub.o: file not recognized: file format not recognized
-> collect2: error: ld returned 1 exit status
-> error: command 'g++' failed with exit status 1
-> ```
->
-> This is caused by `ld` from the Conda environment shadowing the system `ld`. You should use a newer version of Python that fixes this issue. The recommended Python version is 3.8.1+.
-
 **On macOS**
 
 ```bash