Fix typo

src/bin/sfdoc

@@ -35,7 +35,7 @@ usage() {
             "-I PTH, --include PTH  Include path PTH when searching"    \
             "                   for modules; can be specified multiple" \
             "                   times."                                 \
-            "-o PTH, --only-from PTH  Searcho only under path PTH."     \
+            "-o PTH, --only-from PTH  Search only under path PTH."      \
         --                                                              \
         "Without command specified, will try to display documentation"  \
         "in man(1) pager."