patch 8.1.1386: unessesary type casts for lalloc()

Problem:    Unessesary type casts for lalloc().
Solution:   Remove type casts.  Change lalloc(size, TRUE) to alloc(size).
diff --git a/src/diff.c b/src/diff.c
index 3c72e12..7210ce2 100644
--- a/src/diff.c
+++ b/src/diff.c
@@ -710,7 +710,7 @@
     // xdiff requires one big block of memory with all the text.
     for (lnum = 1; lnum <= buf->b_ml.ml_line_count; ++lnum)
 	len += (long)STRLEN(ml_get_buf(buf, lnum, FALSE)) + 1;
-    ptr = lalloc(len, TRUE);
+    ptr = alloc(len);
     if (ptr == NULL)
     {
 	// Allocating memory failed.  This can happen, because we try to read