golangci-lint: switch to fieldalignment

fieldalignment replaces maligned. This currently raises a number of
linting errors because fieldalignment cares about pointer ordering
(for GC); see golang/go#44877 for details.

Fixes: #1252
Signed-off-by: Stephen Kitt <skitt@redhat.com>

.golangci.yml

@@ -11,10 +11,11 @@ linters-settings:
       - unnamedResult
   gocyclo:
     min-complexity: 20
+  govet:
+    enable:
+      - fieldalignment
   lll:
     line-length: 140
-  maligned:
-    suggest-new: true
 linters:
   disable-all: true
   enable:
@@ -39,7 +40,6 @@ linters:
     - ineffassign
     - interfacer
     - lll
-    - maligned
     - misspell
     - nakedret
     - prealloc