unpin flatbuffers and update deps

See: google/flatbuffers#7499

.SRCINFO

@@ -1,7 +1,7 @@
 pkgbase = python-tf2onnx
 	pkgdesc = Convert TensorFlow models to ONNX
 	pkgver = 1.12.1
-	pkgrel = 1
+	pkgrel = 3
 	epoch = 1
 	url = https://github.com/onnx/tensorflow-onnx
 	arch = any
@@ -21,6 +21,7 @@ pkgbase = python-tf2onnx
 	depends = python-onnx
 	depends = python-requests
 	depends = python-six
+	depends = python-flatbuffers
 	source = https://github.com/onnx/tensorflow-onnx/archive/v1.12.1/tf2onnx-v1.12.1.tar.gz
 	source = onnxruntime.diff
 	sha256sums = 77529a4eaa6d50a572020a023af93047b942fbde5cf4447878014037481b7f5f

PKGBUILD

@@ -3,12 +3,12 @@
 pkgname=python-tf2onnx
 epoch=1
 pkgver=1.12.1
-pkgrel=1
+pkgrel=3
 pkgdesc='Convert TensorFlow models to ONNX'
 arch=(any)
 url='https://github.com/onnx/tensorflow-onnx'
 license=(MIT)
-depends=(python python-tensorflow python-numpy python-onnx python-requests python-six)
+depends=(python python-tensorflow python-numpy python-onnx python-requests python-six python-flatbuffers)
 makedepends=(python-setuptools python-build python-installer python-wheel)
 checkdepends=(python-pytest python-graphviz python-parameterized python-yaml python-onnxruntime)
 source=("https://github.com/onnx/tensorflow-onnx/archive/v$pkgver/tf2onnx-v$pkgver.tar.gz"
@@ -22,6 +22,9 @@ prepare() {
   sed -i -r 's#--cov\S+##' setup.cfg
   sed -i "s#'pytest-runner'##" setup.py
 
+  # https://github.com/onnx/tensorflow-onnx/issues/1977
+  sed -i 's#flatbuffers~=1.12#flatbuffers#' setup.py
+
   # The latest upstream tag may not sync with the version file
   echo $pkgver > VERSION_NUMBER