maint: src/*.[ch]: convert more `...' to '...'

Run this (twice):
  git grep -E -l '`.+'\' src/*.[ch] \
    |xargs perl -pi -e 's/`(.+?'\'')/'\''$1/'

1 files changed, 1 insertions, 1 deletions

diff --git a/src/du.c b/src/du.c
index d2759e218..e72ffc9d8 100644
--- a/src/du.c
+++ b/src/du.c
@@ -138,7 +138,7 @@ static bool opt_separate_dirs = false;
 
 /* Show the total for each directory (and file if --all) that is at
    most MAX_DEPTH levels down from the root of the hierarchy.  The root
-   is at level 0, so `du --max-depth=0' is equivalent to `du -s'.  */
+   is at level 0, so 'du --max-depth=0' is equivalent to 'du -s'.  */
 static size_t max_depth = SIZE_MAX;
 
 /* Human-readable options for output.  */