Symbicache fix and documentation typos (#567)

docs/f4pga/modules/index.md

@@ -232,7 +232,7 @@ described in `outputs` should be present.
 
 ### Module initialization/instantiation
 
-In the the `__init__` method of module's class, the following fields should be
+In the `__init__` method of module's class, the following fields should be
 set:
 
 * `takes` - a list of symbolic dependency names for dependencies used by the module

docs/flows/pnr.rst

@@ -34,7 +34,7 @@ step to find more optimal solutions.
 Routing
 =======
 
-Routing is one of the most demanding tasks of the the whole process.
+Routing is one of the most demanding tasks of the whole process.
 All possible connections between the placed blocks and the information on
 the signals propagation timings, form a complex graph.
 The tool tries to find the optimal path connecting all the placed

f4pga/cache.py

@@ -100,4 +100,4 @@ This will cause flow to re-execute from the beggining.""")
     def save(self):
         """Saves cache's state to the persistent storage."""
         with Path(self.cachefile_path).open('w') as wfptr:
-            json_dump(str(self.hashes), wfptr, indent=4)
+            json_dump(self.hashes, wfptr, indent=4)