Revert kfparticle v2 (#741)

Although it was approved by @iraklic and @nigmatkulov and merged by
@fisyak into the main branch, it was deemed premature and not in
accordance with established STAR practices. By executive decision, the
changes in PRs #736 and #734 were reverted to allow @genevb to build a
new library from the main branch.

Author: plexoos

.github/CODEOWNERS

@@ -6,7 +6,6 @@
 /StRoot/PWGTools				                   @nigmatkulov	      @zsweger	   @marrbnl     @lbavinh
 /StRoot/RTS                                        @akioogawa         @jml985      @tonko-lj
 /StRoot/StAnalysisMaker                            @fisyak      @R-Witt        @iraklic
-/StRoot/*KFP*                                      @fisyak      @R-Witt        @iraklic
 /StRoot/StAnalysisUtilities/StHistUtil*            @genevb
 /StRoot/StAssociationMaker/EMC                     @kkauder           @rkunnawa    @Navagyan
 /StRoot/StBFChain                                  @genevb            @plexoos     @klendathu2k @fisyak      @R-Witt        @iraklic

.github/workflows/build-pull-request.yml

@@ -8,14 +8,13 @@ on:
       - '!.github/workflows/**'
 
 concurrency:
-   group: ${{ github.workflow }}-x[${{ github.event.pull_request.number || github.ref }}
+   group: ${{ github.workflow }}-${{ github.event.pull_request.number || github.ref }}
    cancel-in-progress: true
 
 jobs:
   build:
     runs-on: ubuntu-latest
     strategy:
-      fail-fast: false
       matrix:
         starenv: [root5, root6]
         compiler: [gcc485, gcc11]