python3-protobuf: Upgrade 3.11.3 -> 3.12.2

Upgrade to relase 3.12.2. Depends on the upgrade of protobuf
to 3.12.3 in meta-oe. The new release for Python brings:

- [experimental] Added proto3 presence support.
- [experimental] fast import protobuf module, only works with cpp
  generated code linked in.
- Truncate 'float' fields to 4 bytes of precision in setters for
  pure-Python implementation.
- Fixed a memory leak in C++ bindings.
- Added a deprecation warning when code tries to create Descriptor
  objects directly.
- Fix unintended comparison between bytes and string in
  descriptor.py.
- Avoid printing excess digits for float fields in TextFormat.
- Remove Python 2.5 syntax compatibility from the proto compiler
  generated _pb2.py module code.
- Drop 3.3, 3.4 and use single version docker images for all python
  tests.

Signed-off-by: Leon Anavi <leon.anavi@konsulko.com>
Acked-by: Trevor Gamblin <trevor.gamblin@windriver.com>
Signed-off-by: Khem Raj <raj.khem@gmail.com>

meta-python/recipes-devtools/python/python3-protobuf_3.12.2.bb

@@ -7,8 +7,8 @@ LIC_FILES_CHKSUM = "file://PKG-INFO;beginline=8;endline=8;md5=19e8f490f9526b1de8
 
 inherit pypi setuptools3
 
-SRC_URI[md5sum] = "eeda7dea65fc94e560fc9a8180eb1872"
-SRC_URI[sha256sum] = "c77c974d1dadf246d789f6dad1c24426137c9091e930dbf50e0a29c1fcf00b1f"
+SRC_URI[md5sum] = "b4336acee38ebe915b6e72fe8c5bce7b"
+SRC_URI[sha256sum] = "49ef8ab4c27812a89a76fa894fe7a08f42f2147078392c0dee51d4a444ef6df5"
 
 # http://errors.yoctoproject.org/Errors/Details/184715/
 # Can't find required file: ../src/google/protobuf/descriptor.proto