remove redundant slash from list commits api

[aman-harness]

This is causing a CFD: CI-4478 and because of this calls to onprem github fail for listing commits with error:

2022-06-02 00:10:58,536 [task-exec-6] WARN  io.harness.utils.ScmGrpcClientUtils - Scm grpc retry attempt: 1 [accountId=kmpySmUISimoRrJL6NL73w, taskId=q0-Yv7CAQZmm783fvY_Ybg] 
io.grpc.StatusRuntimeException: UNKNOWN: invalid character '<' looking for beginning of value
	at io.grpc.stub.ClientCalls.toStatusRuntimeException(ClientCalls.java:262)
	at io.grpc.stub.ClientCalls.getUnchecked(ClientCalls.java:243)
	at io.grpc.stub.ClientCalls.blockingUnaryCall(ClientCalls.java:156)
	at io.harness.product.ci.scm.proto.SCMGrpc$SCMBlockingStub.listCommitsInPR(SCMGrpc.java:1794)
	at io.harness.utils.ScmGrpcClientUtils.lambda$retryAndProcessException$0(ScmGrpcClientUtils.java:35)
	at net.jodah.failsafe.Functions.lambda$resultSupplierOf$11(Functions.java:284)
	at net.jodah.failsafe.RetryPolicyExecutor.lambda$supply$0(RetryPolicyExecutor.java:63)
	at net.jodah.failsafe.Execution.executeSync(Execution.java:129)
	at net.jodah.failsafe.FailsafeExecutor.call(FailsafeExecutor.java:379)