Merge bitcoin/bitcoin#22102: Remove `Warning:` from warning message printed for unknown new rules

6d7e46ce23 Remove `Warning:` (Prayank)

Pull request description:

  Reason: I noticed that `Warning` is printed 2 times in `-getinfo` while reviewing https://github.com/bitcoin/bitcoin/pull/21832#issuecomment-851004943

  Same string is used for GUI, log and stderr. If we need to add `Warning:` in GUI or other place we can always prepend to this string.

  CLI:

  ```
  Warnings: Unknown new rules activated (versionbit 28)

  ```

  GUI:

  ![image](https://user-images.githubusercontent.com/13405205/120110401-e36ab180-c18a-11eb-8031-4d52287dc263.png)

ACKs for top commit:
  MarcoFalke:
    review ACK 6d7e46ce23

Tree-SHA512: 25760cf6d850f6c2216d651fa46574d2d21a9d58f4577ecb58f9566ea8cd07bfcd6679bb8a1f53575e441b02d295306f492c0c99a48c909e60e5d977ec1861f6

src/validation.cpp

@@ -2251,7 +2251,7 @@ static void UpdateTip(CTxMemPool& mempool, const CBlockIndex* pindexNew, const C
             WarningBitsConditionChecker checker(bit);
             ThresholdState state = checker.GetStateFor(pindex, chainParams.GetConsensus(), warningcache[bit]);
             if (state == ThresholdState::ACTIVE || state == ThresholdState::LOCKED_IN) {
-                const bilingual_str warning = strprintf(_("Warning: unknown new rules activated (versionbit %i)"), bit);
+                const bilingual_str warning = strprintf(_("Unknown new rules activated (versionbit %i)"), bit);
                 if (state == ThresholdState::ACTIVE) {
                     DoWarning(warning);
                 } else {

test/functional/feature_versionbits_warning.py

@@ -21,8 +21,8 @@ VB_TOP_BITS = 0x20000000
 VB_UNKNOWN_BIT = 27       # Choose a bit unassigned to any deployment
 VB_UNKNOWN_VERSION = VB_TOP_BITS | (1 << VB_UNKNOWN_BIT)
 
-WARN_UNKNOWN_RULES_ACTIVE = "unknown new rules activated (versionbit {})".format(VB_UNKNOWN_BIT)
-VB_PATTERN = re.compile("Warning: unknown new rules activated.*versionbit")
+WARN_UNKNOWN_RULES_ACTIVE = "Unknown new rules activated (versionbit {})".format(VB_UNKNOWN_BIT)
+VB_PATTERN = re.compile("Unknown new rules activated.*versionbit")
 
 class VersionBitsWarningTest(BitcoinTestFramework):
     def set_test_params(self):