fix: update requirements.txt

__ISSUE:__
_fix_ - *Update requirements.txt*
\[[#86](https://github.com/danielgatis/rembg/issues/86)\]
__DESCRIPTION:__
The requirements.txt were using strict versioning. While this is not
super bad, it resulted in problems when working on a Mac M1. Mac M1/ARM
still has problems with the scripts, but that's related to pytorch
__CHANGELIST:__
Modified - requirements.txt

requirements.txt

@@ -1,13 +1,13 @@
-flask==1.1.2
-numpy==1.19.5
-pillow==8.0.1
-scikit-image==0.17.2
-torch~=1.7.0
-torchvision~=0.8.1
-waitress==1.4.4
-tqdm==4.51.0
-requests==2.24.0
-scipy==1.5.4
-pymatting==1.1.1
-filetype==1.0.7
-hsh==1.1.0
+flask>=1.1.2
+numpy>=1.19.5
+pillow>=8.0.1
+scikit-image>=0.17.2
+torch>=1.7.0
+torchvision>=0.8.1
+waitress>=1.4.4
+tqdm>=4.51.0
+requests>=2.24.0
+scipy>=1.5.4
+pymatting>=1.1.1
+filetype>=1.0.7
+hsh>=1.1.0