chore(dev/release): Add Python to released source tarball (#372)

Before it had been excluded as experimental/not verified as part of
release verification.
diff --git a/dev/release/source_build.sh b/dev/release/source_build.sh
index 7e1001b..e9fa569 100755
--- a/dev/release/source_build.sh
+++ b/dev/release/source_build.sh
@@ -46,9 +46,6 @@
     cp -R -L "${base_name}.tmp" "${base_name}"
     rm -rf "${base_name}.tmp/"
 
-    # Remove components that are not yet ready for packaging
-    rm -rf "${base_name}/python"
-
     # Create new tarball
     tar czf "${tar_ball}" "${base_name}/"
     rm -rf "${base_name}/"
diff --git a/dev/release/utils-prepare.sh b/dev/release/utils-prepare.sh
index 97b5d86..7ac57f6 100755
--- a/dev/release/utils-prepare.sh
+++ b/dev/release/utils-prepare.sh
@@ -32,7 +32,7 @@
     snapshot)
       local version=${next_version}-SNAPSHOT
       local docs_version="${next_version} (dev)"
-      local python_version="${next_version}dev"
+      local python_version="${next_version}.dev0"
       local r_version="${base_version}.9000"
       ;;
   esac
diff --git a/python/.gitattributes b/python/.gitattributes
deleted file mode 100644
index fea5bc2..0000000
--- a/python/.gitattributes
+++ /dev/null
@@ -1 +0,0 @@
-src/nanoarrow/_static_version.py export-subst