Revert "grpc: update to 1.37.0."

The header grpcpp/impl/codegen/sync.h introduces an dependency on the
abseil header absl/synchronization/mutex.h, but grpc does not install
the abseil headers. Reverting back to v1.36 pending upstream resolution
or a suitable workaround is apparent.

This reverts commit fbe8cadae4.

srcpkgs/grpc/template

@@ -1,7 +1,8 @@
 # Template file for 'grpc'
 pkgname=grpc
-version=1.37.0
-revision=1
+reverts="1.37.0_1"
+version=1.36.4
+revision=2
 _abseilver=6f9d96a1f41439ac172ee2ef7ccd8edf0e5d068c
 build_style=cmake
 configure_args="-DBUILD_SHARED_LIBS=ON
@@ -18,7 +19,7 @@ license="Apache-2.0"
 homepage="https://github.com/grpc/grpc"
 distfiles="${homepage}/archive/v${version}/${pkgname}-${version}.tar.gz
  https://github.com/abseil/abseil-cpp/archive/${_abseilver}/abseil-cpp-${_abseilver}.tar.gz"
-checksum="c2dc8e876ea12052d6dd16704492fd8921df8c6d38c70c4708da332cf116df22
+checksum="8eb9d86649c4d4a7df790226df28f081b97a62bf12c5c5fe9b5d31a29cd6541a
  62c27e7a633e965a2f40ff16b487c3b778eae440bab64cad83b34ef1cbe3aa93"
 
 if [ "$CROSS_BUILD" ]; then