Update puma to 4.3.6 (#1533)

There was a bug on Puma version 4.3.5, causing it to fail when trying to
compile. It was fixed with [#2304].

This commit updates Gemfile.lock and removes the now redundant
explanations on readme.

[#2304]: puma/puma#2304

Co-authored-by: Rob Sanheim <rsanheim@gmail.com>

Gemfile.lock

@@ -307,7 +307,7 @@ GEM
     pry-rails (0.3.9)
       pry (>= 0.10.4)
     public_suffix (4.0.5)
-    puma (4.3.5)
+    puma (4.3.6)
       nio4r (~> 2.0)
     rack (2.2.3)
     rack-attack (6.3.1)

README.md

@@ -75,31 +75,6 @@ rake yarn:install
 rails db:setup
 ```
 
-##### Issues with MacOS Catalina and Puma
-
-When running `bin/setup` on MacOS Catalina, you may encounter issues installing the `puma` gem related to compiler upgrades Apple issued.
-
-If you see errors like this:
-
-```
-compiling puma_http11.c
-puma_http11.c:203:22: error: implicitly declaring library function 'isspace' with type 'int (int)' [-Werror,-Wimplicit-function-declaration]
-  while (vlen > 0 && isspace(value[vlen - 1])) vlen--;
-                     ^
-puma_http11.c:203:22: note: include the header <ctype.h> or explicitly provide a declaration for 'isspace'
-1 error generated.
-make: *** [puma_http11.o] Error 1
-make failed, exit code 2
-```
-
-To fix, install `puma` with this command:
-
-```
-gem install puma:4.3.5 -- --with-cflags="-Wno-error=implicit-function-declaration"
-```
-
-Now re-run `bin/setup` to continue installing everything else.
-
 #### Developing with the Android app
 
 To run [simple-android](https://github.com/simpledotorg/simple-android/) app with the server running locally, you can