lease: fix typos

a. fix typo in godoc
b. make receiver of FakeLessor's function identical

lease/doc.go

@@ -12,5 +12,5 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-// Package lease provides an interface and implemetation for time-limited leases over arbitrary resources.
+// Package lease provides an interface and implementation for time-limited leases over arbitrary resources.
 package lease

lease/lessor.go

@@ -649,9 +649,9 @@ func (fl *FakeLessor) Demote() {}
 
 func (fl *FakeLessor) Renew(id LeaseID) (int64, error) { return 10, nil }
 
-func (le *FakeLessor) Lookup(id LeaseID) *Lease { return nil }
+func (fl *FakeLessor) Lookup(id LeaseID) *Lease { return nil }
 
-func (le *FakeLessor) Leases() []*Lease { return nil }
+func (fl *FakeLessor) Leases() []*Lease { return nil }
 
 func (fl *FakeLessor) ExpiredLeasesC() <-chan []*Lease { return nil }