assocs, math.bitwise: remove first blank line and useless whitespace in a few usage examples

basis/math/bitwise/bitwise-docs.factor

@@ -57,7 +57,7 @@ HELP: bit-clear?
                "HEX: ff 8 bit-clear? ."
                "t"
     }
-    { $example "" "USING: math.bitwise prettyprint ;"
+    { $example "USING: math.bitwise prettyprint ;"
                "HEX: ff 7 bit-clear? ."
                "f"
     }

core/assocs/assocs-docs.factor

@@ -495,7 +495,7 @@ HELP: zip
      { "alist" "an array of key/value pairs" } }
 { $description "Combines two sequences pairwise into a single sequence of key/value pairs." }
 { $examples
-    { $example "" "USING: prettyprint assocs ;"
+    { $example "USING: prettyprint assocs ;"
                "{ 1 2 3 } { 4 5 6 } zip ."
                "{ { 1 4 } { 2 5 } { 3 6 } }"
     }