Add commit to use SPDX copyright headers to git ignore blame revs. (#7381)

Authors:
  - Simon Adorf (https://github.com/csadorf)

Approvers:
  - Jim Crist-Harif (https://github.com/jcrist)

URL: #7381

Author: csadorf

.git-blame-ignore-revs

@@ -33,3 +33,6 @@ b01e2d1d4cf358dbc0a435a663c546fa9cf3e3cb
 
 # Update cython-lint and enforce line length
 99f5ee8770683b51a4fd002781247610aeeaeadb
+
+# Use SPDX for all copyright headers
+6f7a1052f545c7d51d6893ac5791ace574671ed5