Issue #27626: Spelling fixes in docs, comments and internal names

Based on patch by Ville Skyttä.
diff --git a/Objects/longobject.c b/Objects/longobject.c
index 6427f42..ead8f28 100644
--- a/Objects/longobject.c
+++ b/Objects/longobject.c
@@ -556,10 +556,10 @@
         size_t i;
         const unsigned char* p = pendbyte;
         const int pincr = -incr;  /* search MSB to LSB */
-        const unsigned char insignficant = is_signed ? 0xff : 0x00;
+        const unsigned char insignificant = is_signed ? 0xff : 0x00;
 
         for (i = 0; i < n; ++i, p += pincr) {
-            if (*p != insignficant)
+            if (*p != insignificant)
                 break;
         }
         numsignificantbytes = n - i;