Ignore large-scale formatting changes for git blame (quantumlib#5162)

Follow-up to quantumlib#5159 and quantumlib#5160. Ignore these large-scale formatting changes when goind git blame, as suggested by @dabacon.

Author: maffoo

Diff for: .git-blame-ignore-revs

@@ -2,4 +2,10 @@
 a61e51b53612735e93b3bb8a7605030c499cd6c7
 
 # adding flynt formatting for strings
-7a335e3ef297057b4a12f7c21d4e8dd426b44ca0
+7a335e3ef297057b4a12f7c21d4e8dd426b44ca0
+
+# Format cirq-core with latest version of black (#5159)
+cb6940a40141dba95cba84f5acc27acbeb65b17c
+
+# Format cirq-google with latest version of black (#5160)
+77fb93af5ebbb5bcf7f8a4dc3fd2fba0e827488c