Update python-bindings-and-importers.md (#8320)

Exporting PYTHONPATH just post setting it results in overriding it and the .env file already includes the path the 2nd export overrides PYTHONPATH with. So removing the extra export.
diff --git a/docs/website/docs/building-from-source/python-bindings-and-importers.md b/docs/website/docs/building-from-source/python-bindings-and-importers.md
index 82833f5..da04d84 100644
--- a/docs/website/docs/building-from-source/python-bindings-and-importers.md
+++ b/docs/website/docs/building-from-source/python-bindings-and-importers.md
@@ -115,7 +115,6 @@
     # Add ./bindings/python and compiler-api/python_package to PYTHONPATH and
     # use the API.
     source .env && export PYTHONPATH
-    export PYTHONPATH="$PWD/bindings/python"
     python -c "import iree.compiler"
     python -c "import iree.runtime"
     ```