Fix README file (#247)

* Patch README file

Remove incorrect line about updating conda environment

* Fix broken link

Mambda installation page was not found. They changed the docs.

* Fix Flake error C420: unnecessary dict comprehension

Author: edoardob90

README.md

@@ -10,7 +10,7 @@ You have two ways in which you can run the tutorial **locally**.
 
 #### 0. Prerequisites
 
-To run the tutorial locally, you should first install [conda](https://docs.conda.io/en/latest/miniconda.html) (or [mamba](https://mamba.readthedocs.io/en/latest/installation.html)).
+To run the tutorial locally, you should first install [conda](https://docs.conda.io/en/latest/miniconda.html) (or [mamba](https://mamba.readthedocs.io/en/latest/installation/mamba-installation.html)).
 
 It is also suggested that you have a recent version of `git`. Check out [how to install `git`](https://git-scm.com/book/en/v2/Getting-Started-Installing-Git) on your operating system.
 
@@ -67,12 +67,6 @@ Finally, launch JupyterLab with
 jupyter lab
 ```
 
-To update the existing environment, run
-
-```console
-conda env update -f environment.yml
-```
-
 ### 2. With Docker
 
 > **Note**

tutorial/tests/test_control_flow.py

@@ -194,7 +194,7 @@ def test_find_triplet(nums: List[int], function_to_test) -> None:
 
 def reference_cats_with_hats() -> int:
     """Solution with dictionaries"""
-    cats = {i: False for i in range(1, 101)}
+    cats = dict.fromkeys(range(1, 101), False)
 
     for loop in range(1, 101):
         for cat, has_hat in cats.items():