CI: Configure SSL_CERT_DIR to satisfy Python 3.11 on macOS

-- https://stackoverflow.com/q/50236117#comment122846071_50236117

Root cause::

  Error: Error downloading extends for URL https://cdn.crate.io/downloads/releases/cratedb/x64_mac/crate-5.0.1.tar.gz:
  <urlopen error [SSL: CERTIFICATE_VERIFY_FAILED] certificate verify failed: unable to get local issuer certificate (_ssl.c:992)>

Author: amotl

.github/workflows/nightly.yml

@@ -23,6 +23,7 @@ jobs:
     env:
       CRATEDB_VERSION: ${{ matrix.cratedb-version }}
       SQLALCHEMY_VERSION: ${{ matrix.sqla-version }}
+      SSL_CERT_DIR: /etc/ssl/certs
 
     steps:
       - uses: actions/checkout@v3

.github/workflows/tests.yml

@@ -24,6 +24,7 @@ jobs:
     env:
       CRATEDB_VERSION: ${{ matrix.cratedb-version }}
       SQLALCHEMY_VERSION: ${{ matrix.sqla-version }}
+      SSL_CERT_DIR: /etc/ssl/certs
 
     steps:
       - uses: actions/checkout@v3