conformance: add notes about changed mypy behavior in 1.20.0 (#2255)

Addressing a couple comments on #2254 that came in after the PR was merged.

Author: rchen152

conformance/results/mypy/dataclasses_descriptors.toml

@@ -1,5 +1,6 @@
 conformant = "Partial"
 notes = """
+Assumes descriptor behavior only when field is assigned in class body.
 Does not correctly evaluate type of descriptor access.
 """
 output = """

conformance/results/mypy/tuples_type_compat.toml

@@ -1,6 +1,7 @@
 conformant = "Partial"
 notes = """
 Does not support tuple narrowing based on `len()` type guard (optional).
+Incorrectly marks a match case as unreachable.
 """
 output = """
 tuples_type_compat.py:15: error: Incompatible types in assignment (expression has type "tuple[float, complex]", variable has type "tuple[int, int]")  [assignment]

conformance/results/results.html

@@ -814,7 +814,7 @@ <h3>Python Type System Conformance Test Results</h3>
 <a class="test_group" href="https://typing.readthedocs.io/en/latest/spec/dataclasses.html">Dataclasses</a>
 </th></tr>
 <tr><th class="column col1">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;dataclasses_descriptors</th>
-<th class="column col2 partially-conformant"><div class="hover-text">Partial<span class="tooltip-text" id="bottom"><p>Does not correctly evaluate type of descriptor access.</p></span></div></th>
+<th class="column col2 partially-conformant"><div class="hover-text">Partial<span class="tooltip-text" id="bottom"><p>Assumes descriptor behavior only when field is assigned in class body.</p><p>Does not correctly evaluate type of descriptor access.</p></span></div></th>
 <th class="column col2 conformant">Pass</th>
 <th class="column col2 conformant">Pass</th>
 <th class="column col2 partially-conformant"><div class="hover-text">Partial<span class="tooltip-text" id="bottom"><p>* Assumes descriptor behavior only when field is assigned in class body</p><p>* Doesn't allow non-data descriptors or data descriptors with differing `__get__` and `__set__` types</p></span></div></th>
@@ -1030,7 +1030,7 @@ <h3>Python Type System Conformance Test Results</h3>
 <a class="test_group" href="https://typing.readthedocs.io/en/latest/spec/tuples.html">Tuples</a>
 </th></tr>
 <tr><th class="column col1">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;tuples_type_compat</th>
-<th class="column col2 partially-conformant"><div class="hover-text">Partial<span class="tooltip-text" id="bottom"><p>Does not support tuple narrowing based on `len()` type guard (optional).</p></span></div></th>
+<th class="column col2 partially-conformant"><div class="hover-text">Partial<span class="tooltip-text" id="bottom"><p>Does not support tuple narrowing based on `len()` type guard (optional).</p><p>Incorrectly marks a match case as unreachable.</p></span></div></th>
 <th class="column col2 partially-conformant"><div class="hover-text">Partial<span class="tooltip-text" id="bottom"><p>Incorrectly marks a match case as unreachable.</p></span></div></th>
 <th class="column col2 conformant">Pass</th>
 <th class="column col2 conformant">Pass</th>