Merge bitcoin#32252: [29.x] doc: minor rel notes changes

87e5378 doc: minor rel notes changes (fanquake)

Pull request description:

  Remove two unused headers.
  Remove the empty-template, as point releases will modify `release-notes.md`.

ACKs for top commit:
  jonatack:
    LGTM ACK 87e5378
  janb84:
    ACK [87e5378](bitcoin@87e5378)

Tree-SHA512: 69ff0d7863c1598ab2b4daf2a7f9ca3edae513a7d5ebb85aa1b468150cfd17da2f503ac0a41dc77fe04c3670cb7d58df46b00837d08aad624f024756f575fca1

Author: fanquake

doc/release-notes-empty-template.md

@@ -132,10 +132,6 @@ replace-by-fee the standard behavior. (#30592)
 
 - The default for `-rpcthreads` has been changed from 4 to 16, and the default for `-rpcworkqueue` has been changed from 16 to 64. (#31215).
 
-### Wallet
-
-### GUI Changes
-
 ### Build System
 
 The build system has been migrated from Autotools to CMake: