Update Puma to fix chunked upload failures

Older verisons of Puma had a bug where chunked uploads would result in
an empty body:

puma/puma#1839

This breaks OBS file uploads that rely chunked transfers, which is
generally the standard mechanism used by http clients for uploading
large files. A fix was backported to 4.3.7:

puma/puma#2496

so this PR updates Puma to the latest 4.3.x release to include this
fix.

Likely fixes openSUSE#9329.

(Note that, if OBS is behind a reverse proxy, this issue may not be
observed in the first place, as many reverse proxies will tend to
buffer the uploaded data, thus side-stepping the use of chunked uploads
entirely.)

Signed-off-by: Ryan Gonzalez <ryan.gonzalez@collabora.com>

src/api/Gemfile.lock

@@ -282,7 +282,7 @@ GEM
       byebug (~> 11.0)
       pry (~> 0.10)
     public_suffix (3.1.0)
-    puma (4.3.5)
+    puma (4.3.12)
       nio4r (~> 2.0)
     pundit (2.0.1)
       activesupport (>= 3.0.0)