doc: Use relative hyperlinks in release-process.md

Improves usability with offline clones of the documentation.

Refs
bitcoin/bitcoin#30025 (comment)

Author: Jeremy Rand

doc/release-process.md

@@ -6,8 +6,8 @@ Release Process
 ### Before every release candidate
 
 * Update release candidate version in `CMakeLists.txt` (`CLIENT_VERSION_RC`).
-* Update manpages (after rebuilding the binaries), see [gen-manpages.py](https://github.com/bitcoin/bitcoin/blob/master/contrib/devtools/README.md#gen-manpagespy).
-* Update bitcoin.conf and commit changes if they exist, see [gen-bitcoin-conf.sh](https://github.com/bitcoin/bitcoin/blob/master/contrib/devtools/README.md#gen-bitcoin-confsh).
+* Update manpages (after rebuilding the binaries), see [gen-manpages.py](/contrib/devtools/README.md#gen-manpagespy).
+* Update bitcoin.conf and commit changes if they exist, see [gen-bitcoin-conf.sh](/contrib/devtools/README.md#gen-bitcoin-confsh).
 
 ### Before every major and minor release
 
@@ -28,7 +28,7 @@ Release Process
 
 #### Before branch-off
 
-* Update translations see [translation_process.md](https://github.com/bitcoin/bitcoin/blob/master/doc/translation_process.md#synchronising-translations).
+* Update translations see [translation_process.md](/doc/translation_process.md#synchronising-translations).
 * Update hardcoded [seeds](/contrib/seeds/README.md), see [this pull request](https://github.com/bitcoin/bitcoin/pull/27488) for an example.
 * Update the following variables in [`src/kernel/chainparams.cpp`](/src/kernel/chainparams.cpp) for mainnet, testnet, and signet:
   - `m_assumed_blockchain_size` and `m_assumed_chain_state_size` with the current size plus some overhead (see