[BUG FIX] Fix validation of COPY options FORCE_NOT_NULL/FORCE_NULL

Applying: Improve incorrect COPY options tests.
Using index info to reconstruct a base tree...
M	src/test/regress/expected/copy2.out
M	src/test/regress/sql/copy2.sql
Falling back to patching base and 3-way merge...
Auto-merging src/test/regress/sql/copy2.sql
CONFLICT (content): Merge conflict in src/test/regress/sql/copy2.sql
Auto-merging src/test/regress/expected/copy2.out
CONFLICT (content): Merge conflict in src/test/regress/expected/copy2.out
Patch failed at 0001 Improve incorrect COPY options tests.

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"