Recommend pipx as easiest installation method for all OSes and remove…

… warning about apt (#1889)

* Remove warning against installing pipx through apt (1886)
* Remove brew recommendation and consolidate pipx instructions (1888)

docs/installation.md

@@ -7,24 +7,14 @@ License: https://www.gnu.org/licenses/gpl-3.0.html
 
 ## Installation
 
-On Mac and Linux, the easiest way to install `jrnl` is using
-[Homebrew](http://brew.sh/):
-
-``` sh
-brew install jrnl
-```
-
-On other platforms, install `jrnl` using [Python](https://www.python.org/) 3.10+ and [pipx](https://pipxproject.github.io/pipx/):
+The easiest way to install `jrnl` is using
+[pipx](https://pipx.pypa.io/stable/installation/)
+with [Python](https://www.python.org/) 3.10+:
 
 ``` sh
 pipx install jrnl
 ```
 
-!!! note
-     `pipx` should be installed through either `brew` or `pip`. Missing dependencies and other issues
-     may occur when installing `pipx` through `apt` or another package manager. Further installation
-     instructions can be found in [pipx's documentation](https://pipxproject.github.io/pipx/installation/).
-
 !!! tip
      Do not use `sudo` while installing `jrnl`. This may lead to path issues.