PYSEC-2021-424/PYSEC-2021-425/PYSEC-2021-436: Replace short commit ids (#257)

https://ossf.github.io/osv-schema/#affectedrangestype-field requires them
to be "full-length Git commit hashes".

Author: progval

vulns/matrix-synapse/PYSEC-2021-424.yaml

@@ -23,7 +23,7 @@ affected:
     repo: https://github.com/matrix-org/synapse
     events:
     - introduced: "0"
-    - fixed: cb35df940a
+    - fixed: cb35df940a828bc40b96daed997b5ad4c7842fd3
   - type: ECOSYSTEM
     events:
     - introduced: "0"

vulns/matrix-synapse/PYSEC-2021-425.yaml

@@ -19,7 +19,7 @@ affected:
     repo: https://github.com/matrix-org/synapse
     events:
     - introduced: "0"
-    - fixed: cb35df940a
+    - fixed: cb35df940a828bc40b96daed997b5ad4c7842fd3
   - type: ECOSYSTEM
     events:
     - introduced: "0"

vulns/matrix-synapse/PYSEC-2021-436.yaml

@@ -21,7 +21,7 @@ affected:
     repo: https://github.com/matrix-org/synapse
     events:
     - introduced: "0"
-    - fixed: 91f2bd090
+    - fixed: 91f2bd0907f1d05af67166846988e49644eb650c
   - type: ECOSYSTEM
     events:
     - introduced: "0"