completions: fix mixed tab/spaces indentation (#1473)

These templates use 4 spaces for indentation, but some lines
used tabs.

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

zsh_completions.go

@@ -250,7 +250,7 @@ _%[1]s()
 
 # don't run the completion function when being source-ed or eval-ed
 if [ "$funcstack[1]" = "_%[1]s" ]; then
-	_%[1]s
+    _%[1]s
 fi
 `, name, compCmd,
 		ShellCompDirectiveError, ShellCompDirectiveNoSpace, ShellCompDirectiveNoFileComp,