fix: update pinning for libxml2 due to conda-forge migration (#903)

bioconda_utils/bioconda_utils-conda_build_config.yaml

@@ -32,6 +32,13 @@ bamtools:
 r_base:
   - "4.3.*"
 
+# Note: this is a (hopefully) temporary fix for the r-base 4.3 migration. That package was built 
+# with libxml2 2.11, but that migration on conda-forge isn't yet complete. Consequently conda-forge-pinning
+# still has libxml2 2.10. That means that there are a number of R and Bioconductor packages we can't currently
+# build without manually changing out libxml2 pinning.
+libxml2:
+  - "2.11.*"
+
 python:
   - 3.10.*  *_cpython
   - 3.9.*  *_cpython