Fix doc review findings

Users following the info.rst example would get an error
because --config is not a valid flag; fix to --config-file.

The ecbuild URL in requirements.rst was empty.

The install command passed both --prefix and
-DCMAKE_INSTALL_PREFIX, which contradict each other and
confuse newcomers; drop the redundant CMake variable.

The CLI index table listed "grib2fdb" but the binary is
grib2fdb5; align the table so users can find the tool.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: Ozaq

docs/fdb/cli_tools/index.rst

@@ -60,7 +60,7 @@ General Purpose Tools
      - Delete FDB databases and the data they contain.
    * - :doc:`fdb write <write>`
      - Insert data into the FDB, creating databases as needed.
-   * - :doc:`grib2fdb <grib2fdb>`
+   * - :doc:`grib2fdb5 <grib2fdb>`
      - Insert GRIB data into the FDB (legacy tool).
 
 Special Purpose Tools

docs/fdb/cli_tools/info.rst

@@ -60,5 +60,5 @@ Get location of FDB schema file in an easily parsable form:
 Get location of current FDB configuration file in an easily parsable form:
 ::
   
-  % fdb info --config
+  % fdb info --config-file
   <path>/testcases/fdb5/fdb5_simple.yaml

docs/fdb/content/installation.rst

@@ -22,7 +22,7 @@ Now proceed with installation as follows:
    cd $builddir
 
    # 2. Run CMake
-   ecbuild --prefix=$installdir -- -DCMAKE_INSTALL_PREFIX=</path/to/installations> $srcdir
+   ecbuild --prefix=$installdir -- $srcdir
    
    # 3. Compile / Install
    make -j10

docs/fdb/content/requirements.rst

@@ -11,4 +11,4 @@ Runtime dependencies:
 Build dependencies:
 
 :CMake: For use and installation see http://www.cmake.org/
-:ecbuild: ECMWF library of CMake macros ()
+:ecbuild: ECMWF library of CMake macros (https://github.com/ecmwf/ecbuild)