doc: sparse-checkout: Fix list markers

Changed the list markers from a mix of "(1)" and "(b)" to a
consistent numeric format "(1)", "(2)" for clarity and consistency.

Signed-off-by: onee-only <[email protected]>

Author: onee-only

Documentation/technical/sparse-checkout.adoc

@@ -66,7 +66,7 @@ sparsity patterns: patterns from $GIT_DIR/info/sparse-checkout used to
 	reasons: (1) users in cone mode specify directories rather than
 	patterns (their directories are transformed into patterns, but
 	users may think you are talking about non-cone mode if you use the
-	word "patterns"), and (b) the sparse specification might
+	word "patterns"), and (2) the sparse specification might
 	transiently differ in the working tree or index from the sparsity
 	patterns (see "Sparse specification vs. sparsity patterns").