Remove redundant DISTINCT when GROUP BY already guarantees uniqueness

Applying: Rebase UniqueKeys onto master (Andy Fan v3 + Houska 0002-0004)
Using index info to reconstruct a base tree...
M	src/backend/nodes/list.c
M	src/backend/optimizer/path/allpaths.c
M	src/backend/optimizer/path/equivclass.c
M	src/backend/optimizer/path/joinrels.c
M	src/backend/optimizer/path/pathkeys.c
M	src/backend/optimizer/plan/analyzejoins.c
M	src/backend/optimizer/plan/initsplan.c
M	src/backend/optimizer/plan/planner.c
M	src/backend/optimizer/util/plancat.c
M	src/backend/optimizer/util/relnode.c
M	src/include/nodes/pathnodes.h
M	src/include/optimizer/paths.h
M	src/test/regress/expected/join.out
M	src/test/regress/parallel_schedule
M	src/test/regress/sql/join.sql
Falling back to patching base and 3-way merge...
Auto-merging src/test/regress/sql/join.sql
Auto-merging src/test/regress/parallel_schedule
Auto-merging src/test/regress/expected/join.out
Auto-merging src/include/optimizer/paths.h
CONFLICT (content): Merge conflict in src/include/optimizer/paths.h
Auto-merging src/include/nodes/pathnodes.h
Auto-merging src/backend/optimizer/util/relnode.c
Auto-merging src/backend/optimizer/util/plancat.c
Auto-merging src/backend/optimizer/plan/planner.c
Auto-merging src/backend/optimizer/plan/initsplan.c
Auto-merging src/backend/optimizer/plan/analyzejoins.c
Auto-merging src/backend/optimizer/path/pathkeys.c
Auto-merging src/backend/optimizer/path/joinrels.c
Auto-merging src/backend/optimizer/path/equivclass.c
CONFLICT (content): Merge conflict in src/backend/optimizer/path/equivclass.c
Auto-merging src/backend/optimizer/path/allpaths.c
Auto-merging src/backend/nodes/list.c
Patch failed at 0001 Rebase UniqueKeys onto master (Andy Fan v3 + Houska 0002-0004)

error: Failed to merge in the changes.
hint: Use 'git am --show-current-patch=diff' to see the failed patch
hint: When you have resolved this problem, run "git am --continue".
hint: If you prefer to skip this patch, run "git am --skip" instead.
hint: To restore the original branch and stop patching, run "git am --abort".
hint: Disable this message with "git config advice.mergeConflict false"