clean up more dead code

  - SkSHA1 is unused
  - SkRunnable is obsolete now that we have std::function

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1705583003

Review URL: https://codereview.chromium.org/1705583003
diff --git a/tests/PathOpsThreadedCommon.h b/tests/PathOpsThreadedCommon.h
index 5bf5da2..54586d9 100644
--- a/tests/PathOpsThreadedCommon.h
+++ b/tests/PathOpsThreadedCommon.h
@@ -8,7 +8,6 @@
 #define PathOpsThreadedCommon_DEFINED
 
 #include "SkGraphics.h"
-#include "SkRunnable.h"
 #include "SkTDArray.h"
 
 #define PATH_STR_SIZE 512
@@ -44,7 +43,7 @@
     skiatest::Reporter* fReporter;
 };
 
-class PathOpsThreadedRunnable : public SkRunnable {
+class PathOpsThreadedRunnable {
 public:
     PathOpsThreadedRunnable(void (*testFun)(PathOpsThreadState*), int a, int b, int c, int d,
             PathOpsThreadedTestRunner* runner) {
@@ -73,7 +72,7 @@
         fTestFun = testFun;
     }
 
-    void run() override {
+    void operator()() {
         SkBitmap bitmap;
         fState.fBitmap = &bitmap;
         char pathStr[PATH_STR_SIZE];