docs: restore missing verb in blas/ext/base/sdiff README

The strided example introduction dropped the verb "compute",
producing "to differences of every other element". Match the peer
`ddiff` README wording so the sentence is grammatical.

Ref: 7c287ff

Author: claude

lib/node_modules/@stdlib/blas/ext/base/sdiff/README.md

@@ -68,7 +68,7 @@ The function has the following parameters:
 -   **workspace**: workspace [`Float32Array`][@stdlib/array/float32]. Must have `N + N1 + N2 - 1` elements.
 -   **strideW**: stride length for `workspace`.
 
-The `N` and stride parameters determine which elements in the strided array are accessed at runtime. For example, to differences of every other element:
+The `N` and stride parameters determine which elements in the strided array are accessed at runtime. For example, to compute differences of every other element:
 
 ```javascript
 var Float32Array = require( '@stdlib/array/float32' );