Remove the keepOriginalHeader retry loop

The loop is pointless for two reasons:
- git apply --3way has this fallback built in already. If it can't do a
  three-way merge, it will fall back to applying the patch normally.
- However, the only situation where it does this is when it can't do a 3-way
  merge at all because it can't find the necessary ancestor blob. This can only
  happen if you transfer a patch between different repos that don't have the
  same blobs available; we are applying the patch to the same repo that is was
  just generated from, so a 3-way merge is always possible. (Now that we fixed
  the bug in the previous commit, that is.)

But the retry loop is not only pointless, it was actually harmful, because when
a 3-way patch fails with a conflict, git will put conflict markers in the
patched file and then exit with a non-zero exit status. So the retry loop would
try to patch the already patched file again, and this almost certainly fails,
but with a cryptic error message such as "error: main.go: does not exist in
index".

pkg/commands/patch/patch_manager.go

@@ -255,21 +255,12 @@ func (p *PatchManager) ApplyPatches(reverse bool) error {
 			continue
 		}
 
-		var err error
-		// first run we try with the original header, then without
-		for _, keepOriginalHeader := range []bool{true, false} {
-			patch := p.RenderPatchForFile(filename, true, false, reverse, keepOriginalHeader)
-			if patch == "" {
-				continue
+		patch := p.RenderPatchForFile(filename, true, false, reverse, true)
+		if patch != "" {
+			err := p.applyPatch(patch, applyFlags...)
+			if err != nil {
+				return err
 			}
-			if err = p.applyPatch(patch, applyFlags...); err != nil {
-				continue
-			}
-			break
-		}
-
-		if err != nil {
-			return err
 		}
 	}