Test Encyclopedia: Document TEST_WORKSPACE behavior

It's now unconditionally set by Bazel, however not documented as such.

RELNOTES: none
PiperOrigin-RevId: 247986215

site/docs/test-encyclopedia.html

@@ -238,9 +238,6 @@ <h3>Initial Conditions</h3>
     <tr><td><code>TEST_SRCDIR</code></td><td>absolute path to the base of the runfiles tree</td><td>required</td></tr>
     <tr><td><code>TEST_TOTAL_SHARDS</code></td><td>total shard count, if sharding is used</td><td>optional</td></tr>
     <tr><td><code>TEST_TMPDIR</code></td><td>absolute path to a private writable directory</td><td>required</td></tr>
-    <tr><td><code>TEST_UNDECLARED_OUTPUTS_DIR</code></td><td>absolute path to a private writable directory (used to write undeclared test outputs)</td><td>optional</td></tr>
-    <tr><td><code>TEST_UNDECLARED_OUTPUTS_ANNOTATIONS_DIR</code></td><td>absolute path to a private writable directory (used to write undeclared test output annotation .part files).
-
     </td><td>optional</td></tr>
     <tr><td><code>TEST_WARNINGS_OUTPUT_FILE</code></td><td>absolute path to a private file in a writable directory (used to write test target warnings)</td><td>optional</td></tr>
     <tr><td><code>TESTBRIDGE_TEST_ONLY</code></td><td>value of <a href="user-manual.html#flag--test_filter"><code>--test_filter</code></a>, if specified</td><td>optional</td></tr>